Front Forks on your BMW Airhead motorcycle.
Front fork alignment, stiction, braces, gaiters, springs.
Cleaning & lubricating steering head bearings.
Replacing steering head bearings. Modifications.
Avoiding fork tube twisting. SETTING FORK SAG.
In-depth discussion of STICTION & ALIGNMENT.
HINTS regarding fork internals.
Adjusting the swing arm.
item #54, sub-section 10A
© 2014, R. Fleischer
There is a substantial difference between some of the BMW fork designs. The /5 Airheads forks are very different from those of the 1980's, for an example. The GS forks are again different. Rather than do something like Clymers books have done, which is to just show sketches for every model, I decided to select one popular type, & expand upon its internals & its operation. I show hints & details for the /5 & other forks, scattered throughout this article. In this first section is a sketch & description of how the 1981-1984 forks operate, some information about the modifications the FACTORY did during production to REDUCE NOISES & IMPROVE OPERATION, etc. There were THREE stages of these changes. While the factory never identified these as stages, I, as others have, identify them as Mk1, Mk2, & the final as Mk3. AFTER 1984, many of the forks used MUCH of the Mk3 design. The below photo of a sketch is of the 1981 fork, but with the last version of the factory modifications, which I call Mk3.
The 1981 forks were of a very different design than previously. They also made a lot of clicking & clunking noises! BMW's first fix was to install SHIMS below the valve body, which did reduce noise. The rebound spring above the damper valve rattled, but relatively quietly. This change lasted into 1982. Then came a new valve with shortened length body & a special tabbed (on upper face) spring washer, used to force the valve body against the top recess of the original orifice plate. This change was probably done primarily to eliminate hand-shimming in production. Another modification was to eliminate the original steel washer that controlled the oil flow. Instead a thick Teflon ring was used, which fit tighter & was quieter. The upper face of the valve body was machined to fit the thicker ring, & movement was thereby restricted, between bump and rebound, giving MORE bump damping.
The final change, shown in this sketch, which I call the Mk.3, came in 1983. The valve mechanism was SHORTENED, and the bottom had a recess containing a spring, same as the rebound spring. This prevented any oscillation. It also improved the fork operation during AGGRESSIVE transitions between bump & rebound conditions. The springs also improve the operation of the hydraulic 'stop'. Because of how these forks are designed, it is very important that the oil have very good anti-foaming characteristics.
The over-all damping is dependent upon oil viscosity. Certain characteristics of fork operation are dependent on fork oil level (fork oil amount). BMW lowered fork oil levels, republishing specifications. Those who modify the forks for one or another purpose know about these things, & more.
That article includes oil information charts and covers Airheads and Classic K bikes.
How these forks work: When you hit a bump in the road, the 'slider' (fork lowers) go upwards, & oil moves from the lower area inside the fork, through the gap between the piston rod & the valve body. The valve ring pushes against the orifice plate, & oil moves to the upper chamber area by means of the gap under the ring. THE GAP ITSELF IS THE RESTRICTION. On REBOUND, the piston descends & oil is forced against the ring, sealing it to the valve body. The oil path is the small orifice at the upper end of the piston rod, which passes oil MORE SLOWLY than the gap below the ring, thus providing stiffer rebound damping. As the slider descends, the lower chamber becomes larger in volume, & oil comes from inside the piston rod, via the orifice at the LOWER end of the rod. The gap below the valve ring & the upper piston rod orifice determine the relationship of bump & rebound damping(s).
Fork Internals....MORE DETAILS:
The early forks contain what BMW calls "wiper rings" buried inside the
mechanism. These look like small versions of common piston rings.
I HIGHLY RECOMMEND that you do NOT replace them. New rings from BMW
are NOT properly made, do NOT fit correctly, give too much friction. OLD
ones generally will work BETTER than new ones, since they slide easier.
Any minor extra oil leakage due to wear is usually MINIMAL!
You may want to take a look at:
John Chay, who manufactures an Airhead cylinder stud threaded hole repair jig, has a fair amount of information on various parts for early & late Airhead fork parts, Works Performance Springs, etc.
HINT: Pressing in the top stanchion seal is sometimes a hassle. Try heating the stanchion to around water-boiling temperature, & if you do not have the proper BMW tool, use an appropriate-sized socket for pressuring.
BMW has had at least FOUR service bulletins on the new style internals front forks that appeared in 1981. Some summary information here....
First bulletin: Prior to the 1981 model, BMW offered a heavy duty front fork spring number 31-42-1-232-017 for use when fairings were installed...BMW did this themselves for the RS and RT models. For 1981 BMW added a SPACER, rather than change the fork spring. The spacer is also called an Intermediate Ring, and is part 31-42-1-241-737. You need two of them for the bike. You then needed a longer bolt, and the bolt at the fork bottom was changed to a M12 x 40, part 07-11-9-919-767, and you should replace the associated seal ring used with that bolt, and it is a 12 x 15.5, part number 07-11-9-963-130.
Bulletin of July 1982: BMW tried to fix front fork CLICKING NOISE.
was 31 007 82 (2046). This bulletin advised the fitting of shims, which were available
in various sizes from 0.5 to 1.1 mm thickness, to remove the play between the valve
housing and the retaining circlip. One was to use one or more shims as required. There was a circlip unit change, as the earlier one with tongues to keep the damper
body from moving was not doing its job.
Another part of this bulletin was for fork spring rattling inside the fork tube. There was
supposed to be a white nylon plastic spacer used on BOTH ENDS of the spring.
Implied was that if one or both were missing, they were to be installed.
The Bulletin (these are called SI's by BMW mechanics...as the title is
Service-Information) of July 1983 was strictly to show a revised fork oil amount for
all the models, and a list of approved fork oils. I have the correct information for you
in an article:
The Bulletin of August 1983 31 009 83 (2082) advised that for all models EXCEPT the R65 and R65LS, the fork dampers were now changed. NO LONGER were the shims, see above paragraph, being used. The fix by BMW was with a new spring-loaded valve housing, which eliminated axial play that caused noises. NOTE!.....the valve washer has a CHAMFER....the chamfer is installed TOWARDS THE PERFORATED DISC. BMW advised that whenever the forks lacking this updated valve housing were serviced, that it be installed. The backside of the bulletin had a sketch of the valve disk washer, housing, spring, ring, and retaining ring, as how fitted. The backside also had a sketch of the special tool to compress the valve housing spring so you can install the retaining ring. You can improvise something. The 1981+ forks have a rubber washer in the damper valve. Remove and discard. The may be a spacer in the bottom (RS/RT) that raises the fork height. If you fit new springs, especially aftermarket ones, and the height/sag is wrong, remove the spacer. Be sure the compression damping piston is TIGHT on the damper rod, and use Loctite Blue on these.
re: Damper rings 31-42-1-234-506 and 31-42-1-232-045: You will see these items listed on sketches, and they are used in two places on each fork side. The top one is for compression damping, used with the holes (orifices) in the rod. After the fork is compressed, it will rebound, and the spring-loaded disc keeps the center passageway from providing oil movement, so the rebound damping is from what oil that moves between the damper rod and the LOWER damper ring. The 3 pieces involved were originally just 1 threaded ring, so don't get confused by the various diagrams and sketches. BMW has a nasty habit of showing, on its sketches, every part ever used. There are two types of damper rings used for the LOWER rings...so, yes, that means two types of REBOUND types. The normal force ring is 31-42-1-232-045, and on most sketches this is item #9. Just below, on most sketches, is item #10. BMW's information on what is used on what models can be very confusing with the forks. Ring -506 is called the STRINGENT ring by BMW (more damping, the SPORT ring that is), it is identified by the groove that is machined on the outside diameter...which is used only for identification purposes (in the same way that the valve seat inserts have a groove marking for the cylinder heads, for the change in valve seat material, from 1985). The -506 damper ring also can be identified by its smaller inside diameter, which is 15.5 mm (the standard ring, the -045, is 15.7 mm inside diameter). Again...BOTH RINGS ARE NOT USED AT THIS POINT. One uses either the Stringent -506, or the standard -045, at the LOWER position. THE TOP RING IS ALWAYS THE -045. ...two are used on the bike.
NOTE: the -045 damper ring is not used on stock /5 front forks. On the /6, it subs for the 31-42-1-232-058. So...what rings should you use? If you have the heavy duty front fork springs from BMW, 31-42-1-232-017, then use the -506 damper rings. NOTE that slightly heavier oil might be a good idea with this combination. Maybe an equivalent 7 SAE. Note also, that these -017 fork springs can sometimes be identified by having a white paint marking. They are 4-1/4 mm in coil diameter; and the length, when new, is 543 mm. The other springs, the slightly softer ones, are 31-42-1-231-358, and they have 4.0 mm coils, and when new have a length of 567 mm...yes, that is correct, they are LONGER, yet SOFTER.
For the /5 bikes, some modifications can be done that can be very helpful. Using the floating rings, & updated threaded rings: braze closed one or preferably two of the rod holes (there are 4 total in each rod).
HINTs: Some sketches may show an O-ring, or washer, 31-42-1-240-027, or it might be 31-42-1-232-763. Some sketches may show a 31-42-2-000-384, typically as item #7, a bumper, located below the spring. The sketch, as noted above, can be confusing. The damper piston goes between the spring and the bumper cushion. When disassembling, you'll likely find that bumper is around the rod. The bumpers deteriorate. The FLAT SIDE goes UP.
Don't willy-nilly change parts unless you THINK first. If you mostly ride on smooth roads, and are heavy, then I would suggest the Stringent damper rings, slightly heavier oil, and the -017 springs. Some very aggressive & lighter riders might like the changes too....especially if coupled with a stiff custom top triple clamp. If your roads are rather bumpy, you might find, especially if a lighter weight rider, that the heavy duty springs & stringent damper rings are too much; the ride will be too stiff, not work well on bumpy roads.
After 1980/1981, these part numbers & usage do not apply like I have shown here!
A superb article on motorcycle front fork
That article was done by Randy Glass. Lots of images. Highly recommended! This is the GOLD STANDARD for basic motorcycle fork alignment. I had a small hand in helping a bit.
***Periodically I check this, but, the above link will NOT work properly in the
various browsers (Chrome, I.E., Firefox) I have checked it on. It DOES seem
to display the opening page with credit to Randy Glass. The forward arrow
is NOT working.
The problem is, I think, that the article was written using a
very old version of Microsoft FrontPage & Arachnophobia. Duane was informed
years ago about this.
However, I was informed, on 12/01/2015, that the following link will now work:
YES: That does work 12/01/2015, but does not identify the author on that first page, although the forward arrow for further pages DOES work.
If you STILL have problems, then
I suggest that you try the following link, which
avoids you trying to play with code & settings to TRY to get it to work:
You may be intimidated by the article. It IS comprehensive and detailed; but.... it is not a difficult job. Randy's article, which was written as he worked on his BMW Airhead quite some time ago is/was so good that I never wrote one like it myself, I just refer folks to it. I admit to some contributions to Randy's article. The photos really tell you what you need to know if you wanted to get into it in depth. But, whether you do a complete job like Randy spells out, or not... it is good to know what the proper & best procedures might be. Most will not have forks that are in dire need of the full alignment... but most would be improved considerably. Reading the article will let you know what CAN be done & HOW it is done. You will see as you read the article that some much simpler checks may well be all that you need.
You will also see by example & photos what the very important reverse-torque method is, to avoid twisting your fork tubes. This is particularly important on the models before the last of the Airheads. The illustrations of the anti-torque method are just ONE type. I have some photos that are NOT in that above article, regarding torque & anti-torque tools, & they are later in the article, below, that you are presently reading.
This article applies to most motorcycles with older-style conventional telescopic forks. It is especially so with the smaller tubes & triple clamps that are not very thick nor of larger diameter compared to more modern types. The smaller the thickness & smaller the diameter, the easier it is to twist or warp the tubes. Many top triples are steel plates that sit on top of the tubes. Some other types are clamping types, some have machined recesses, etc. Some are of sturdy aluminum or magnesium alloy castings. The more mechanically strong and/or clamping types with recesses are less likely to allow the tubes to twist or otherwise go out of correct alignment. Many a motorcyclist has ridden with a front fork that has a steel or aluminum flat plate as the top triple clamp, & is quite surprised at the improvement in handling from installing an aftermarket top triple that grips the tubes and is precisely and ruggedly made. Due to the forces from the wheel, at the end of a long lever (that lever is primarily the long tubes), the forces at the top triple can potentially be VERY large, right on up past the lower triple clamp (which is often very much beefier than the top triple clamp). Few folks install a beefed-up lower triple clamp, as usually the lower stock one is quite sturdy. Some of us old-timers remember obtaining an extra lower triple clamp and using that lower triple clamp, modified, as a top triple clamp. Can be a bit ugly, but quite effective. Our biggest problem & reason we used the lower triple clamp for the top, was that machining from a block of aluminum to the accuracy needed was a huge machinist's chore back then. Quite strong aftermarket top triple clamps are available for many motorcycles, but some are poorly machined & can make things worse. Some are wonderfully made!! Some require a bit of ingenuity and work to make them fit properly....such things as headlight mounting ears, or? may require modifications, etc. Today's numerically-controlled milling machines can make these items easily and quickly, ONCE SOMEONE DOES THE PROGRAMMING AND SETUP. MOST folks are surprised at how handling improves with a stiffer top triple clamp as opposed to a stock flat plate. This is not so on all bikes; some come with beefy top triples.
Adding an aftermarket fender brace is often NOT very effective...and if not hand-fitted to avoid stiction effects, CAN MAKE THINGS MUCH WORSE! Usually a stiff top triple does MUCH MORE for handling. IT IS CRITICAL, for best fork operation, that stiction BE MINIMIZED!
The motorcycle manufacturer may well have installed a somewhat less stiff top triple clamp ON PURPOSE, to give a certain FEEL, which is part of the over-all chassis design. For crisper & tauter handling, a stiff top triple clamp is always helpful. I know of no instances where a properly made & installed aftermarket clamp-on top triple clamps does not give better handling & feel on an Airhead... than an original flat steel top triple plate.
Cautions and Warnings: It is rather easy on most telescopic forks to adversely twist the tubes in relationship to each other. That can mean the tubes are not parallel to each other; or, are twisted the other way, or both. A cursory glance at the top and lower triple may make you think this can't happen without actual bending of the tube itself. NOT SO. It takes almost no movement of the tubes in the triple clamps to make the tubes, much lower down, be not parallel, or moved for and aft in relation to each other. Keep in mind that the top & bottom triple clamps are NOT tied to each other EXCEPT by the tubes (the central tube, the steering stem, has little effect), and CAN be twisted, usually this means in the horizontal plane with reference to each other. In a few instances, the triples themselves have been bent, usually from an accident; and this can be very difficult to "see". The primary problem, tubes twisting for & aft or sideways in relationship to each other, can come about from failure to prevent this from happening when loosening & tightening the center nut or tube nuts, at the top triple clamp. It also can come about from faulty installation of the axle; or fender brace or fork brace. I can't tell you how many times I have found improperly installed braces.
NOTE: For information on replacing the
steering head LOCK, see:
Adjusting the 1986-1995 steering head bearings:
I have not written up a separate detailed procedure for
those bikes. Enough information is available at:
HOWEVER, in this boxed section you are reading, are some
hints and details.
The major difference is the use of a sleeve tool on SOME models; which, when properly utilized, MAY
eliminate the need for road tests. There still MIGHT be a necessity for minor adjustments to find out if
the initial adjustment was too loose or too tight, especially if a sidecar is being used.
Note that in these later forks, there are two types and only one uses the
sleeve tool. Anton Largiader's website discusses this adequately.
NOTE that the sleeve adjustment type of forks have an advantage, in that the reverse-torque method needed
to tighten things, to avoid twisting the forks, is NOT NEEDED!
Disassembly/Assembly, last generation of the Airhead forks: SOME of the last of the Airheads, from the mid/late eighties to 1995, had different types of forks. No longer are the fork tubes threaded internally at the top. There is a top plug on each side, and it is held into the tube by an internal expanding clip. Regular circlip pliers won't work as the clip area has beveled edges, etc. Hold the plug with a very large allen wrench and then you can remove the external ring nut. ....remove the clip with the plug pressed against the spring. Fun, huh? On the other hand.... NO counter-torque (anti-torque) method is needed on THOSE types. You will find those on the GS bikes. The RT, for instance, still has the original type of threaded ring adjustment, so an anti-torque method is a good thing to do.
We had a thread about these different fork tubes top style forks in early 2013 on the Airheads LIST; Tom Cutter offered his method & I did some editing & offered mine, etc. The over-all response was something like this: The nut on these models is 41 mm, not 36 mm like on the early models. There is a dogbone wrench available with a 41 mm flat end, see http://bmwmotorcycletech.info/tools.htm . You could use an adjustable wrench too. Hold the central nut with either of those tools, and rotate the center threaded plug CW, to loosen it. Remove the nut and washer, press the center threaded plug down, and release the clip by pushing on it with a dull flat blade screwdriver. The LOWER side of the circlip groove is a bevel, so the clip will move down, tilt, and you can then remove it. The spring is obviously pushing on that circlip. Remove the spring and check the fork tube for rough surfaces. The sealing is done by an O-ring, 31421454962. Be sure the upper edge of the circlip groove is smooth, or it will injure your new O-ring. You should do a fork oil change when working on these forks. You probably are doing the above work to eliminate oil weeping/leaking, by replacing the O-ring. I suggest you fill the fork with the proper amount of oil BEFORE the plug is installed...the center hole is small. BE SURE TO USE fresh gaskets, which are number 07119963073. You are going to be holding the nut, and tightening the center threaded plug, so the torque wrench is used C-CW. Top nut: 40 foot pounds.
NOTE! NO counter-torque (anti-torque) method is needed on these (ONLY!) types of forks when tightening at the center.
Early fork interiors contain what BMW calls "wiper rings". These are quite small piston rings. I HIGHLY RECOMMEND that you do NOT break them & DO NOT replace them unless broken accidentally. New rings from BMW are NOT properly made, do NOT fit correctly, give too much friction. OLD ones generally will work BETTER than new ones, since they slide easier. Any minor extra bypassing oil leakage due to rings wear is usually MINIMAL! These rings are very brittle, so be careful! The early eighties front forks are quite different internally from the earlier forks. When disassembling the early eighties forks, one of the first things you will do is drain the oil and try to remove the bottom parts. Do not try to remove the metal plate.
For longest steering head bearing life you must not only clean & re-grease them now & then, but it is a GOOD idea to move the steering from full left to full right, to help redistribute the grease....I sometimes do that when I park the bike.
It is advisable to read this article completely through before beginning any work on the front end.
The exact procedures vary with the bike model and year....different fitments at the top triple are the primary EXternal differences.
In the February 2003 issue of AIRMAIL, 'Oak' Okleshen,
in an article entitled "Tank
Slappers (from the Airlist)", succinctly identifies and discusses weaving & the high speed
diverging wobble called a tank slapper. He also states his method of adjusting the steering
head bearings. There is an IN-DEPTH article on this website with MY detailed information
on steering wobbles, tank slappers, etc:
The information MAY WELL SURPRISE YOU!!!
FORK OILS: This section has been moved to article 54, sub-section 10B: http://bmwmotorcycletech.info/front-fork-oils-amounts.htm
It is extremely common for riders to not understand fork adjustments. For example, the front fork needs to have proper SAG adjustment. BMW did that at the factory, as an approximation; by what springs it installed. From 1981, BMW began using spring spacers to compensate for sag on some models, rather than spring changes. You MUST have the front suspension in a reasonable sag operating range when you are seated on the bike & the bike has its most normally used loading (you, luggage, passenger if normally carried). Have the bike on the center-stand. The front wheel (tire) must NOT contact the ground. If it does, put a piece of plywood under the center-stand. Either do the following by measurements taken by a friend; or make up a zip tie arrangement on a fork tube to measure the change, or figure your own method. Measure from someplace on the fork lowers, to the upper area, with the tire not on the ground. That is the full-extended value. I use the bottom edge of the lowers myself, up to the bottom of the lower triple clamp. Take the bike off the center-stand. Put a normal load on the bike (you, passenger, luggage, etc.). The forks must compress about 1 to 2 inches. That is a reasonable value, selected out of my hat of experience. If NOT within that range, & you are not going to change springs, remove ONE top cap (top of the upper triple clamp) at a time. Adjust the spacer you may find there. On some models, BMW has inserted a spacer at the top, that sits on the spring...or, up against the 36 mm top slug threaded part. ADD, or shorten, etc., the spacer. On those models with a spacer/adapter that fits in the center of the spring with a nose on it, leave that spacer/adapter intact. ADD a spacer if required. BMW has a spacer, about 5/8", that is 31-42-2-000-399. But, you can make the spacer you need, easily. For the early forks, you can make the spacer you need from 3/4" standard PVC (plastic) pipe, from your nearest plumbing or hardware store. I make mine on a lathe, usually of metal so it looks nice & has squared ends...but you can do it with PVC, or you can make one with a hacksaw, & maybe file the ends nicely square & clean. Install the spacer, then do the other side.
You want to use a spacer that gives you 1 to 2 inches of sag. I prefer closer to 2".
The rear shocks come with adjustable spring perches. That adjustment is not to stiffen the shock, but to level the bike....but, in effect, what you are doing is setting the rear SAG. It is a crude way of compensating for loading, where a different spring would be the better choice, if needed. About 20% of rear shock travel is plenty enough. Most owners will do nothing more than adjust the shock perch stiffer for use with a passenger. Some rear shocks have adjustable bound or rebound, however. Follow the manufacturer's information on them. Sidecarists: The same adjustments apply for front & rear....unless you have a leading link front end....then, there is a lot more to know....and I do NOT get into sidecars in THIS article.
Gaiters: Inquiries about installing gaiters on Airheads that came with gaiters (OR WITHOUT them, such as on a RT) are rather common. Gaiters DO protect the chrome fork tubes from the little nicks they would otherwise get from oncoming small rocks, gravel, etc. Those nicks need to be dressed out now & then, or they will ruin your fork lowers top seals. Some want to install gaiters & can't find them. 11 & 13 rib gaiters are available aftermarket. Rancho Shocks (shocks for cars and trucks) makes various colored gaiters than can sometimes be adapted. The original stock gaiters, on those BMW airheads that came with them, used a roll pin as a air bleed hole (breather). A roll pin is a tiny hardened steel tube, with a small gap up the side, so they have a tiny bit of springy capability if you want to put them in a hole that is very slightly smaller than the roll pin is. The /5 Airhead had 13 ribbed gaiters, fitting well down the fork leg. The /6 bikes had shorter 11 rib gaiters, & were set less far down. With some fork braces you probably will want the 11 rib gator. You will need some sort of air bleed....see next paragraph. If you have an RT, you CAN use the gaiters from such as a R80G/S. The 11 rib gaiters can be used. You CAN keep the fairing rubber bellows; or, you can modify the fairing rubber bellows. Unless the fairing rubber bellows are removed or modified, there will be limited fork travel, side to side. If the bike did not come with gaiters, you may need to install the roll pins (vent pins) 07-11-9-941-470, into the lower triple ...look underneath......there are vertical holes there for that purpose. You need to install them so there is some portion sticking downward...same as the thickness of the -669 ring. The roll pins position the -669 ring, and then the clamps won't crush things. When installing gaiters, you normally remove the flexible bellows-cups in the fairing, and the top black outside covers on the top of the lower fork stanchions.
The parts needed are: 4 each #07-12-9-952-121 clamps, which are size 47 to 54 mm (or common substitutes). 2 each #31-42-1-241-669 rings 2 each #31-42-1-241-666 boots, although you can substitute other types 2 each #07-11-9-941-470 roll pins (maybe) The BMW gaiters fit very nicely & do not need a clamp at the top: 31-42-1-234-908
Airheads AND K-bikes: If you want to install fork gaiters, & want INexpensive but adequate gaiters, you can look at the following website: http://www.gorancho.com/ You can also just enter the following part numbers into Google. You may have to enter the number with or without the "RS": Rancho Shocks, black #RS1952. Quite a few other colors are available, pink, green, etc. Blue is RS1950; Yellow is RS1951; Red is RS1927; Black is RS1952. Available from a wide variety of autoparts places, including NAPA. You may be able to get brand new gaiters FOR FREE, from places that install Rancho steering dampers.
"Stiction" is used to describe a property of two surfaces that are sliding with each other. Stiction, the word, is used by motorcyclists almost exclusively to describe front fork stiffness BEFORE and JUST AT beginning movement. Stiction for front forks on motorcycles, as used by riders, is typically NOT described by some mathematical VALUE (though it can be), but by the perception that the initial force it takes to START the sliding movement is MUCH higher than the force to CONTINUE the sliding. If stiction is high, your forks will not move very well, if at all, when the tire meets small road irregularities. Handling can be very poor. Stiction will greatly affect the comfort and handling over small road irregularities, including lightly bumpy ...as well as very small bumps such as tar snakes size.
Some folks try to compensate for the combined effects of stiff springs, stiction, etc, and often increase the oil amount in the forks, (more often they wrongly increase the oil viscosity). In general, these things cause the handling to get REALLY BAD! I suggest that you use the proper oil & amount, at least initially. Some effort at reducing as much stiction as possible will pay off in big dividends. Stiction can REALLY make you unhappy!
Here are two relatively easy tests for stiction:
(1) Put the motorcycle on the centerstand, & ensure that the front tire is NOT on the ground. Put a zip tie on the upper tube where it meets the lowers. It need be only moderately tight. PUSH HARD on the front end, pressing on the handlebars, this pushes the front tire to the ground & you are pushing the forks, springs & all components. Release, & note where the zip tie has moved to, with the wheel off the ground again.
(2) Now strenuously PULL upwards on the handlebars, and release. The fork will settle at a new position that is NOT where the zip tie is, but above it.
(3) The distance is caused by the stiction. It needs to be minimized.
(4) Remove the front wheel. Re-insert the axle after a THOROUGH cleaning & lubrication. DO NOT use nor tighten the nut. You may have to remove the brake calipers on disc-braked bikes (Do NOT hang them by their hoses!!) in order to remove the wheel. Use the anti-torque method to avoid twisting the forks & unfasten the top tube nuts or whatever is used; remove the springs. You may have to remove the handlebars on some models. YES, the central nut on the top middle is still there & tight. The top is complete, together, just no springs.
(5) Put one hand on each lower fork assembly & slightly move the lowers towards each other, & away from each other. With a nice slippery axle you should see some movement...you should NOT need nor want much force. Find the approximate center of the movement, & leave the lowers at that point. Use your hand & LIFT the axle.... so the lowers, with axle inserted....moves upward. Take it pretty close to the maximum upwards movement. Try both directions, very small & also larger amounts of movement, with lowers fully extended, & testing just above that point...& then with lowers much more upwards. Will always be some stiction...shouldn't change much though. If the stiction is high, you have a problem to investigate. The first thing to try is to unfasten any braces (that includes the fender mounting which acts as a brace), & retry this procedure. If the stiction mostly disappears, you must deal with the braces by bending or washers/shims, whatever is appropriate to YOUR bike. If the stiction does not disappear, you need to get a pane of glass & maybe a dial indicator, & find out just how & how much the tubes are twisted. Once you fix the alignment of the tubes in the triple clamps; you can again check the above method; & then if OK, add a brace or the fender mount;....and as noted you may have to bend or shim at the brace(s). The use of any fender mount or brace MUST NOT affect the stiction...if it makes it worse, you have not done your work properly. It is very important to understand that at every step in the procedures I outline here in this long article, you are advised to continue checking stiction, as you do your work. What I mean by this is that if you do an initial check with the springs out; then, when you have the springs in and the spring caps or clips back on (as, let us say, the next step), REcheck the stiction.
>>> There HAVE been rare instances of a bent top triple plate, or other hard-to see anomaly, so if stiction starts up when you do some particular step in the procedures, then find out why and fix it! Aftermarket braces have been the cause for lots of stiction. SOME aftermarket braces can NOT be adjusted in the plane you would like to. Even if the tubes, triples & braces, etc., are assembled correctly, you can add stiction by not equalizing the lowers on the axle before tightening the fork lowers axle clamps. BMW has always recommended that before any front axle clamps are tightened, you bounce the front end on the ground (push the handlebars), centering the lowers on the lubed axle; THEN tighten the axle clamps.
Note that some of the factory braces are OK, & the hoop braces of CC Products were OK, & can even be superior to the Telefix. Tubular braces can be re-bent or otherwise played with....with such as washers... to eliminate stiction/binding of the forks! The Telefix type is used in conjunction with the stock fender mount which is a brace, more....or less.....depending on the model. ANY form of fender or fork lowers bracing MUST be checked for smooth operation of the lowers.
A sturdy upper triple plate almost always does much more for handling than a fork brace. If the lowers are badly worn, the brace may help considerably. Some bikes came with stiff cast top triple plates, such as the R65, etc. Others have a steel plate, that is not as good, IMO. You may have noticed Airheads with top triple modifications, courtesy of one of our Club Members (Toaster Tan) who designed & had them machined. He still makes & sells them. CC used to sell several types of top triple clamps, fork braces, etc. Luftmeister sold some types as well. I caution on the use of them, some I've seen don't seem precisely made. A fork can be aligned with parallels & a dial indicator, although a piece of plate glass does amazingly well; that is with the wheel/axle/fork brace NOT in place. The Randy Glass article I cited at the top of this page is a good primer. When the long procedure is not done....what I do is as follows:
FIRST!...HAVE NO SPRINGS INSTALLED & NO WHEEL INSTALLED. If the tubes are pitted badly, strongly consider cleaning up those pits, as any proud metal will wear the seals quickly. Be sure the front axle is cleaned of any crud/rust/etc. If need-be, use steel wool, sandpaper, wire wheel, whatever. It needs to be smooth, & the LOWERS need to be clean too, in the hole for the axle. If there are any bits of proud metal on the lowers or axle, remove them!
Install just the oiled axle loosely into & across the lowers, with NO springs in the forks.
Lift the axle upwards & see how smoothly it operates (I may well put a dial indicator between the tubes when doing it but not always). There should be no appreciable change during the lifting over just about the full range. The triples may need adjustment to obtain that lack of stiction.
The fork/fender brace(s) are then installed. These can really upset the alignment, so shimming, hand re-work, bending, whatever, depending on the type, is sometimes needed. Once installed properly, there should AGAIN be no change as the axle/lowers (still no spring, no wheel), is lifted up & down.
At that point I install the wheel, LIGHTLY grease the axle & install it & the axle spacers. Then I tighten the axle nut, equalize the lowers on the axle, & THEN I tighten the pinch bolt(s).
The front end should now still be very smooth with no added friction. Then I reinstall the springs & caps. When all is back together, consider checking the sag. A properly installed fork brace will mask problems with worn fork lowers, & in that respect will help. For most fork braces, properly installed, there is a stiffening effect, noticeable in some types of riding, particularly bumpy cornering & some other situations, that helps, but not greatly. A massively & carefully built fork brace, properly installed, can make a difference. Generally, the heavy dual-hoop tubular ones are better. Any that are not made very well, or distort the forks upon installation, will make the handling WORSE!
A better top triple clamp, in many instances, does far more for handling. Both a stiff top triple.....and....a good properly installed fork brace ....are, together, a good thing.
If you install new BMW wiper rings inside the fork, you may have problems...they do not fit properly, have high friction too. Use the old ones! If you broke the originals, make sure the ones you install have a decent amount of ring gap.
The steering head bearing is common type 32028, 28 x 52 x 16 mm. BMW has used this number on all the Airheads, & even the Classic K-bikes! BMW dealerships have all sorts of prices for that bearing. There are variations on the 32028 part number, you may find 320/28X & other things. The bearing may be listed as I.D.: 1.102"; O.D. 2.047"; width: 16 mm. You can purchase a bearing almost anyplace, even a local auto-parts store, which MIGHT list it as a A-32 bearing. Just ask for a tapered roller bearing, & provide these numbers. Prices will be MUCH cheaper than many BMW dealerships ask. Swing arm bearings are 30203A, 17 x 40 x 12 mm; and are basically the same as MOST of the pre-1985 wheel bearings, which are 30203. The difference is sealed versus unsealed. Frankly, I like them UNsealed, at both places. Every few years I remove the entire rear end, and hand clean those bearings. If I am working on a bike and find sealed ones, I puncture the seal, or otherwise remove or disable the seal, so I can get proper greasing in the future from & into the 6 mm Allen adjuster hole. My comments for the steering head bearings pricing & where to buy, above, APPLY for the most part to the swing arm bearings & wheel bearings too.
Steering Head Bearings: If you feel a notch in the steering, particularly at or close to straight-ahead with front tire off the ground, THIS IS OFTEN HARDENED GREASE, ....perhaps 70% of the time). This very long section includes information on replacing the bearings, and also on just cleaning and re-lubricating, which often is all that is needed to eliminate the notchiness.
The bearing puller, Kukko or similar, works very nicely. A Kukko is not cheap, and a few adapters are needed for shop use. Due to the cost, many use other methods, depending on what they might have or have access to. The use of an electric welder to create a hot spot or a bit more around the lower steering neck inner race, and thereby enable cracking/shrinking it, works OK, it just falls out. For the top race, a similar use of a welder works fine too, and you can weld something to it, to lift the bearing out....a couple of 'fender washers' perhaps. The use of a Dremel, or other high speed tool with an abrasive disc to cut nearly through the outer race, then a tap with a hammer and chisel, also works OK, but takes a fair amount of time...and discs. Additional information on seal pullers and bearing pullers, including much cheaper ones, are item 22 in this article: http://bmwmotorcycletech.info/tools.htm
The reason these various things are done is because the bearing outer race fits in a shelf, & you cannot use a long drift tool from the other end of the steering stem to knock out the bearing outer race.
The steering stem tube itself is fitted into the lower triple clamp, and MY advice is, STONGLY, that it should NOT BE REMOVED. If you do, you MUST heat the triple, & you will need to INDEX the stem during replacement, EXACTLY (heated triple again), otherwise you will not have the lock slot in the correct position. If you press or bang the stem out withOUT heating, you could RUIN the fitment; & you COULD end up with constantly, forever, changing steering adjustments. This problem of an ever-changing need for adjustment IS ALSO caused by simply reinstalling the tube in what you hope is the same position. The factory manuals will show that the lower triple clamp, maybe it will be called a lower fork bridge, is heated to sizzle temperature (100°C or 212°F); then you drive (soft hammer or piece of wood & hammer) the tube downwards; then reinsert the tube without the bearing IMMEDIATELY; then heat the bearing & install.
Please avoid trouble.. DO NOT do it the way the factory recommended, BUT, do it one of MY ways:
There are several methods I approve of, that will keep you out of trouble. One is to use a Dremel or similar rotary tool; cut the bearing & then use a hammer & chisel on the cut. If you are careful, that works fine. You can remove the pesky lower bearing on the steering stem by snipping off the bearing cage and thus removing the rollers.
Oak fills the stem (using a cork to stopper the bottom) with ice cube chips, about 1/2 to 2/3 from the bottom, then heats the race QUICKLY & instantly then pries up the bearing using two very large broad screwdrivers. You will have to reheat the bearing again after it is removed upwards enough, to enable full removal (I do it upside down). You can also fashion a method with a puller to do the whole job.
When installing the new bearing, heat it, on a flat metal plate, until the bearing actually measures water sizzle temperature or a BIT higher; put the dust shield in place & the new bearing, tap the bearing into place with a sleeve tool. It helps to freeze the yolk first, which shrinks, slightly the tube assembly. Before you do any of this, look at the bottom of the yolk where the stem fits into.
Notice a small space, where the tube was not pressed all the way down. ~1/16". That is what you want to maintain....so when using the sleeve tool use a large flat washer to be sure the yolk does not move. You tap the bearing downwards, fully into place, using your sleeve tool. If the bearing is fully tapped home, you won't be bothered by constant adjustments. Main thing is to NOT let the stem move in the lower triple!...in any part of this procedure. Another method is to heat the triple, moving the steering stem just enough to, after cooling, get two screwdrivers between the bearing and triple, then you can pry up the bearing off the stem. You can then RE-heat and reset the stem depth. NOTE that this will usually ruin the lower dust cap, so order a LOWER dust cap ahead of time. You don't absolutely have to have a dust cap, of course, but I recommend you do.
is another method: you can
purchase aftermarket tools specifically designed to service the steering
Ask on the airheads list for the latest vendor information.
When installing the new outer races, I do it with the old outer race, or, a steel part I made in my lathe for the purpose, or, I may just use an appropriate size of socket. Use of a large size long piece of All-Thread from the hardware store, and large heavy washers or sockets & washers, etc, will also do the job just fine. Be VERY sure that the outer races area of the steering stem are dead clean of any foreign matter...right into the edge where the bearing fits. Be VERY sure that the outer races are seated 100.0% fully...otherwise you will be adjusting them over & over, as road pounding, etc., cause them to seat further inwards & your steering loosens. Not a good idea, especially at high speeds, if too loose. Keep in mind that 0.001" makes a difference.
Use a NON-moly grease on the steering bearings.
Recheck the adjustment after some miles. If you installed the outer races properly, & did not mess up the stem fitment, the adjustment will be stable.
Plan on cleaning & regreasing every few years (just lower the steering an inch or so).
NOTE: Occasionally someone asks something like this: "When removing the outer races of the steering head bearings with the 'tack-welding procedure' is it sufficient to just to disconnect/remove the battery to protect the electronic/electric circuits or are there other protective steps required?
This is my reply: Yes, disconnect one side of the battery. But....AFAIK there have been no reported incidents of problems with any Airhead of any year. However, in the instances (every one of these was at a TechDay) where I have used a stick welder to enable cracking of the outer races, I make sure all aftermarket electronics devices are disconnected. I unplug the turn-signal flasher relay (later ones have electronics), disconnect the plug from the instrument pod (except /5), and I remove the front cover on the electronic ignition models and disconnect the three pin plug to the canister... then I use aluminum foil or other means to short-circuit the three pins together (canister side). I disconnect the ignition module plug. It is quite likely not necessary to do all these things, but I have done them anyway, as extra insurance against problems. BTW, I ground the welder at the opposite outer race.
Cleaning and re-greasing steering head bearings:
Cleaning and re-greasing the steering head bearings may eliminate "notchiness" that seems to indicate the need for new bearings & races. It is likely best to do this procedure soon after installing new, balanced tires, as road crown, squaring wear, and balance, will have an effect on trying to make final on-the-road adjustments. Shops do not clean & re-grease steering head bearings, they simply replace them. The reason is labor costs, if the cleaning & re-greasing then shows the bearing to still be poor in feel. YOU don't have that labor cost limitation, right? In a SHOP situation, labor is THE expense for the customer, and having to clean, assemble, adjust, and then find out that the bearings are still notchy...can be a waste of time &, thereby, customer money. In a home situation, with you doing the work, it is only another hour (two at the most, including doughnuts & coffee breaks) to try cleaning, inspection, relubrication, partial re-assembly & preliminary adjustment. If you then find the steering still notchy, you do not have all that much more work to remove the front end, because you have only retightened the top adjustment nut for a check... no need to install nor tighten the top acorn nut, assemble the bars/cables, etc. If you remove the top area, & the inner bearing, & look at the cleaned outer race, and see vertical marks & if you can feel them with a fingernail, REPLACE THE BEARINGS.
Cleaning & lubrication of the steering head neck bearings is not a difficult job, but if a bearing is found truly bad, replacing the bearings & outer races is considerably more labor intensive, as one must deal with fairings, brake components, cables, removal of the entire front end, ....how to remove the bearings, ....etc.
Contrary to some popular belief, our BMW steering head bearings of the tapered 'Timken' style may well last over 200,000 miles. If the bearings & their races are in good condition & properly greased & adjusted, the steering will be light, smooth, without notches. Notches almost always are in the straight ahead position. Cleaning/greasing is critical for not only hardened grease problems, but for protecting the bearings from moisture, which ruins them. The upper & lower dust cups help to protect the bearings. You likely will not find out if the bearings are bad until you first try the cleaning & greasing & simplified adjustment. The differences between airheads is mostly minor, with improvements after the /5 models in the parts used to adjust the bearings; and, later, changes in the top of the top triple fitments.
Cleaning & re-lubrication is recommended every 30,000 miles, especially with the open non-faired models, & particularly if driven often in the rain. Depending on grease, time, and mileage, cleaning & re-greasings may be 5 or 10 years apart, in reasonable conditions.
Do not use greases containing moly (molybdenum disulfide) compounds. My experience with moly is that it does not work properly in this application. Almost any light grease will be OK. It is desirable to use a grease with good smearability, good water resistance, & particularly a low evaporation/hardening over time. I use Chevron NLG1 or NLG2 Ultra Duty EP, a red colored grease, available from a Chevron Distributor, & not likely at your local Chevron gas station. Typically "they" want you to purchase a small box of these grease gun tubes. This grease can be mixed with about 30% moly (or Staburags or Optimol) & used for clutch & rear end splines...but don't use that mixture at the steering head or other tapered type roller bearings; nor, for ball bearings. The plain unmodified grease is also very good for automotive chassis & U-joints. BMW red grease is "OK". Generally speaking any thin non-fibrous grease will likely work reasonably well.
EARLY Airheads, such as unconverted stock /5 bikes, used a somewhat different adjusting method for the adjustment ring just under the top triple clamp. Many have converted them to the later non-split ring type. The adjustment on the earlier type is done with a small diameter rod that is part of the tool kit, & is a slight bit of a PIA, but doable.
In our society of sue-crazy individuals, the following disclaimer applies:
I take no responsibility for the following procedure, nor for any ineptness on your part, such as failure to tighten things!... etc. Airhead Canon #8 (and others) applies!
I originally developed & wrote this procedure using both a 1983 R100RT & 1984 R100RT. YOUR bike may be different, but the basics still apply.
1. Remove the gas tank. Avoid scratching the paint, especially watch for interference with the opened seat: the left front edge of the metal seat pan is not nice to your tank paint. If there is a problem with interference, remove the seat. With the tank removed, now is a great time to inspect wiring, nuts, bolts, perhaps even the starter motor, breather, whatever. I usually recommend you service the electrical system contacts, plugs, sockets, ETC....even cleaning the ignition coil(s) at this same time you have the tank off. Heck, service those fuel taps (petcocks). If you have a damper knob, remove damper knob center screw, remove knob, spring, plastic spacer.
2. If you have the BMW hydraulic steering damper, you will need to disconnect the forward, large end, at the fork adjustment area ball. If you have a BMW fairing, you must first remove the small rectangular rubber plug at the fairing, you will re-glue it into place when all done. Then rotate & remove the damper wire clip (the wire clip, if you are not familiar with it, is the same as used on the shift linkage of many models). To remove the wire clip you must rotate it off the shaft where it is clipped to, then it will pull out of a tiny hole in the damper ball socket. Do NOT loose that wire clip. Pay attention as to where & how it fits. DO NOT try to force the ball & socket apart if you have not removed the wire clip, you WILL break the ball socket. Once the wire clip is removed, the damper forward ball socket will pull down off the ball. It might be somewhat frozen to the ball, you might then have to force it off with such as a screwdriver blade. Push the damper backwards, so it collapses. When reassembling this area, you should clean & lubricate the various damper parts, including oiling or moly greasing the ball.
3. Remove the dress cover at the handlebars if you have one. Remove the instrument pod assembly if you have one, by first unscrewing the speedometer cable 'nut' at the cable/pod & then remove the cable. Loosen only the 3 each 10 mm headed bolts holding the pod to its bracket. You do NOT have to remove those three bolts. While you are in this area, note if you have WHITE colored rubber vibration isolators. If so, replace with the updated, probably BLACK ones, from your dealer, they will reduce instrument vibration, prolong instrument life, and probably keep the needle intact. Lift up & remove the instrument pod from the bracket & remove the phillips type screw at the center of the pod's electrical connector & wiggle out the cable/connector. Set the pod aside where you won't trip over it. When reinstalling the plug, spray a small amount of contact cleaner-lubricant or silicone spray into the contacts. If corrosion is noted, remove the corrosion, as best & as neatly as you can.... before using cleaner or spray.
4. Using a substantial sized hammer if you have to, and the BMW tool kit 36mm flat spanner (you CAN hit that wrench with a large hammer on its sides), and being careful not to damage the ignition module if you have one, loosen completely the 36mm top stem CAPNUT. This is a bit different on the later models. Do NOT loosen the lower triple clamp clamping bolts at this time! You want to avoid twisting the forks. Below is a photo showing just one method of using an anti-torque tool; for TIGHTENING mode. This same idea, photo courtesy and permission to use here, from Randy Glass ..see article noted above in:
In the photo below, the screwdriver tip seems to be pressuring the large closed end wrench (also called the BMW DogBone wrench) on the right side, this is not so. The photo shows the wrench and screwdriver for the TIGHTENING direction, but simply move the screwdriver shank to to the other side of the upper pin (or shoulder bolt, or whatever you use) and the other side of the crown nut, for LOOSENING.
I have taken the liberty of modifying this photo I obtained from Randy, see the TWO RED arrows showing force direction.
HINT: the flat spanner dogbone wrench can be put over the damper rod (on some models), or otherwise slipped over the cap nut (many models), and you will NOT have handlebar interference, if the flat end of the spanner is THINNED a bit. Do that on a grinding wheel and DO NOT thin very much, and DO NOT take the temper out of the metal by getting it too hot. With the spanner now able to fit, in almost every instance, it may not be necessary to remove the handlebars from the top triple plate, nor even loosen them for steering adjustments. For cleaning and re-greasing, you do have to remove the bars, but still attached to the upper triple clamp! Another method of making an anti-torque tool is to use a pry bar or very strong screwdriver BETWEEN the handlebar mounts (leaving them in place for this).
Below are 4 more photos, that may be helpful to you. These are to give you ideas of various means to do the loosening and tightening of the center top cap and the fork tube caps, and the triple clamps, etc....so as to avoid or correct twisting, ETC.
The "procedure" continues after these photos.
This same squared-off end is done to 27 mm or 1-1/16" sockets, for the swing arm locknut. You can use a short socket, as above photo, for the front fork tubes' caps, and with the wood piece as shown, the cap can be hand-pressured so the threads are not injured when removing OR replacing the top cap. Frankly, Snowbum uses the dogbone wrench.
A piece of bent pipe that is being used to apply torque in one direction, with the top triple clamp in place.
For torque applied the other direction:
**If you have not removed the ignition module (1981+) in a long time, cleaning and re-greasing it with heat sink compound... why not do this now?, after all, you have the fuel tank off, right? I suggest you clean the starter relay connections too, if you have the starter relay that plugs-in.
The bike must be jacked up a bit to have the front tire off the ground a couple of inches. You can jack it at the front of the engine, or perhaps at the front exhaust pipe crossover. The bike will rest on the center-stand and the rear tire. How this is done is up to you, and it may vary between bikes depending on tire size, suspension components, condition of those components. Some folks park the bike on a sidewalk, with the front end over the curb. On a flat floor, a specific problem will usually arise if you have a ride-off center stand. For such, I will usually jack the bike at the rear of the engine/transmission...or at the rear frame crossover...or the exhaust pipes (wood across them both) near the muffler junction. I have also, depending on the situation, placed a goodly sized piece of 1" thick plywood near the center stand, lined it up with my eyeball, and with the bike on the SIDEstand, place the plywood into needed position, and then straighten up the bike and engage the center stand UPON the plywood. This works well on ride-off stand equipped bikes. I have done all sorts of things to get the front wheel off the ground a couple of inches....on a few bikes with Reynolds RideOff stands, I have used locking straps at the rear suspension, to squeeze the rear suspension down...I usually add such straps from the lower shock units eye, up to some place like the luggage rack center area,,,,jump on the seat, whilst tightening the strap. The front wheel will now be quite far off the ground.
Block the front forks from dropping down too much, with wood or similar under the tire, if you need to.
5. Remove, being careful with that hammer on the dogbone wrench! (if you need a hammer), the 36mm hex tops from the top of each fork tube at the top of the upper triple clamp plate. USE an anti-torque method. Be careful, use downward pressure, there may be substantial spring pressure here! It is not necessary to remove the caps center allen head bolts, where you put oil into the forks normally. With the left and right top caps removed, and the acorn nut removed, you can now lift the handlebar assembly and tilt it enough to clear the damper rod (if you have one) in the stem . Fasten the handlebar assembly forward against any windscreen, etc. or however; using some padding and a long bungee cord wrapped around the windscreen...or just lay it forward, depends on the bike. It is not necessary to remove the fork springs. So, at this point, you have a handlebar with controls & cables & top triple as a total assembly lifted off the stem, & a front end ready to be dropped an inch or more. Now you can remove the adjustment nut that was under that cap-nut using the BMW tool kit wrench. Remove the dust shield. /5 models and late models are a bit different, but reasonably self-explanatory. /5 models can be updated with the easier to adjust /6 type adjustment ring, etc.
6. You now must remove the block of wood or whatever, if anything, you had under the front tire. A pull, sometimes a goodly JERK, from below, on the forks lowers, will release them downward a tad (adjust wood under the fork as required). If need be use a piece of protective hardwood (not metal) on the top of the steering stem, & the hammer, & give this a decent whack. When the fork drops down, say a couple of inches, then adjust the wood block(s) below the forks to move the fork very slightly up. This is necessary as the forks will have to be wobbily-moved-around a bit fore & aft sideways, during the cleaning & greasing operation, so you can get your cleaning rag, & finally your greased fingertips, into the lower bearing area. The top bearing is right there & EASY to deal with.
7. EXTENSIVELY & THOROUGHLY CLEAN THE LOWER BEARING/RACE AREA. Use lots of lint free rags. I prefer old pieces of cotton bed sheets cut into strips about 1-1/2 or 2 inches by maybe 12 inches, so as to wrap well around the bearing during the cleaning. Use a small amount of a solvent such as kerosene or paint thinner on the rag pieces. Do NOT use dripping wet amounts. Clean as best you can the entire bearing, innards, the shell, & area surrounding. You should be able to rotate the entire bearing, & get a good cleaning. Move the fork as required. Then a final cleaning with a dry LINT FREE rag. Grease this lower bearing. I use my fingers & a LOT of grease, forcing it up into the outer race & the bearing, rotating the bearing as required. You can not, easily, use too much grease. You will need to use some finger pressure to force the grease into the bearing; rotate the bearing, & push grease into it; & onto the outer race in the steering stem. Be generous with the grease, you will clean the area up after final reassembly. Force as much grease as you can, all around & into the lower bearing, & leave a goodly amount in the stem outer race area. NOTE: If you have the hydraulic damper on your bike, this is a GOOD time to lubricate the plate/rack area that drives the ball when the damper is adjusted from the top knob. You can put the knob alone back in place on the damper rod, rotate the adjustment, get some oil/grease into that plate/rack area at the very bottom of the lower triple clamp.
8. Remove the upper bearing rotating part, clean it & the cup/shell/race area. There should be no roughness felt while rotating it. If there is, add a few drops of oil, if then OK, then the bearing, if it LOOKS OK, probably is, so you can now hand grease the bearing, forcing grease throughout.
It is important that stiction not be introduced by your work, and any stiction minimized. Earlier in this article I described a test with the springs out, and advised that as you reinstalled them and the caps, that you recheck stiction. Depending on what you are doing to the front end of the Airhead, you may want to be testing for stiction as you reassemble; during the steering head adjustment, during reinstalling of the fender or other braces and mounts and wheel assembly, brake, ... whatever, ...depending on what the various things you are doing to the bike. Do NOT let excessive stiction be in YOUR bike!
REASSEMBLY AND ADJUSTMENT:
Note: if you are cleaning & relubricating, & doing a quickie test to see if your bearings really are needing replacement, you can just install the adjustment threaded ring (other models have other adjustment methods) and make a simple temporary adjustment on the fork bearings, so you can feel the steering. You need NOT tighten the adjustor very much, so NO reverse-torque techniques are needed. You do NOT have to assemble the bars with the controls and cables assembly, etc. If you then find notchiness, undo the adjustor, remove the front end entirely, for new bearings. New bearings ALWAYS means a complete set of bearings with their matching outer races. NEVER replace just an inner bearing.
Assuming your tests are good:
1. Put top bearing, shield cup, adjuster nut, etc., in place, lifting/blocking the fork upwards, then lightly tighten the adjuster nut, using the special hook wrench (or, whatever, depending on your model). Wiggle the fork as need be. Attach the handlebar/top triple plate assembly. You should now be able to attach the center top nut, or acorn cap nut, ETC., depending on your model. If that cap nut has a ridge underneath that is to engage the hole in the top triple clamp plate, be SURE it fits into the hole in the plate. Attach the fork top 36mm hex plugs/nuts with any washers. Doing this can take considerable grunt against spring pressure; it will help to use a screwdriver (or?) into the allenbolt recess to apply downward pressure. Do not cross-thread! HINT: It is easiest to start the top hex plug caps with the front wheel/tire as low as it can go, yet high enough to enable a few threads to be engaged. This means a minimum amount...three threads or so, of the center nut.
NOTE:your bike may have a strange plastic spacer at the top of the springs. That spacer is formed to fit to the cut end of the coiled spring, so be sure it is put onto the spring properly...LOOK at it, and see how it goes together. SOME people use a piece of PVC pipe (or metal spacer) at the top to provide extra preload, I am NOT talking about that here. NOTE that those using pieces of pipe, etc., for "preload" are REALLY changing the SAG of the front end. Be SURE you know what you are doing if playing with spacers.
DO NOT FAIL to loosen the lower yoke (lower triple-tree casting) Allen bolts, that provide the clamping pressure on the fork tubes. Do NOT loosen those lower yolk pinch bolts before having top nuts in place. The usual reason to loosen, and later retighten, those lower triple side-clamping-bolts, is to allow the tubes to move ever so slightly, as you adjust the top bearing. Do NOT forget to tighten them after you are done.
Be sure all is lined-up correctly and tighten the two 36mm hex fork tube plugs to a small fraction of a turn LOOSE from hand-wrenching tight. No need for the anti-torque tool right now unless you want to;...you are NOT tightening to the limit. I DO use the anti-torque tool, taking no chances here.
2. Tighten the adjustment nut, that is UNDER the top plate (late models are done differently), rather tightly, moving the fork back and forth to take up any grease spacing. Loosen, and retighten moderately tight. You now have to tighten the top acorn cap, as tightening it will tighten up the adjustment of the steering stem....see later herein. You DO need the anti-torque tool for this, as the acorn nut, whilst not 100% tightened in this step, DOES need VERY substantial tightening, to remove the 'play' in the ADJUSTOR'S threads. SO.....you need NOT make this the final tightening at this time, which is QUITE tight; still, that center top cap must be rather tight. Maximum hand effort is about right, using the dogbone wrench, and the anti-torque tool...and NOT with the forks against mechanical stops!.
NOTE: Most acorn capnuts have a ridge along its bottom, that MUST fit into the top triple clamp hole...be sure it does!...if you do NOT have that properly assembled, you will bend things!
The motorcycle should be on the center stand and the front tire not touching the ground, nor any block of wood, etc. If the forks flop easily to one side, unscrew the top cap, tighten the underside adjustment, retighten the top cap. Try to get the forks so they JUST BARELY won't fall to one side by themselves; move the forks lightly from stop to stop to distribute the grease better, and try again.
There are rare instances in which proper preload on the steering head is not obtained without grossly excessive tightness on the adjustor. The adjustment may not be stable, & need readjustment over time. You have done things properly, such as loosening the lower triple clamp during adjustment. The top acorn nut fits properly & is not worn where it fits into the top plate. You may or may not have replaced the upside-down chromed metal cup at the top bearing area. What is going on?
The chances are good that the chrome cup is getting trapped in the stem threads. This can ALSO happen with a faultily-made chrome cup. Be sure it fits correctly, & especially if a new one, file the center so it does not hang-up on the threads.
3. Inspect to be sure that wiring, cables, etc., do not interfere with front end movement. Assemble everything except, generally, the gas tank and steering damper and pod. Leave the lower triple clamp allen clamp screws loose for now, but tighten up the top triple plate at the fork tube 36 mm hextops. You NEED the anti-torque tool. The motorcycle should still be on the center stand and the front tire not touching the ground, and NO block of wood, etc.
4. The first try for a final adjustment, for motorcycle, not sidecar use, should be to the point that the front end exhibits a SMALL amount of perceptible drag. The only friction should be from stem bearing grease, a small amount of bearing drag, fork tubes rubber boots if you have those, and cables/wiring. Give a 'rap' on a handlebar end, using your palm. This should be of sufficient force to move the handlebar about an inch or more, but not go flying to the stops. The handlebar will probably tend to just barely reverse direction a TEENY amount, or not quite, after such a rap. Another way of looking at this is that the steering, once somewhat to one side or the other from center, should want to not really quite fall to the side, especially if nudged. You must temper this idea with friction from cables and the rubber fairing boots, etc. It is a bit better to start from a bit too tight, as that will be seen as weaving at low speeds, and a heavy feeling to handling. Your bike will vary SLIGHTLY from other Airheads, in this adjustment. GENERALLY, you will want the forks on such as the G/S and R80ST and most naked (no fairing) bikes to just fall almost all (or actually all) the way to one side, but not so on the RS, RT, both of which need to be a bit stiffer.
Those with sidecars attached should set the steering head tighter than even the RS/RT as noted; there must be NO tendency for the fork to continue to move towards the stops, or to fall to one side or the other after being nudged on a sidecar rig. This is quite important for sidecarists.
At this point, turn the bars slowly from fully right to fully left. If you feel roughness or a center notch, you need new bearings & races!
5. At this point tighten the top 36 mm fork nuts & cap nut FULLY...as tightly as you can with your hand & the flat wrench, & then several taps more with the hammer. USE the anti-torque tool. The center cap nut has to be near final tightness. You will notice the capnut has a major effect on the adjustment nut setting, so loosen the capnut & readjust the adjustment nut, then retighten the capnut....until conditions are correct, with how that fork moves when nudged.
6. Final check, with the CAP nut tight, if you turn the bars one way or the other, from the straight ahead position, & nudge them, they should NOT QUITE fall very much, just a small amount on RS/RT, & DO just barely fall to one side on other models. Some may want it a bit lighter, have the fork JUST fall, almost fully or fully, to one side, but NOT too easily. Those with no fairing boots will likely want it a tad looser. A tad of friction is better, but if it causes more than a WEE bit of weaving at low low speeds, it is too tight. Those with GS & ST bikes may not want weaving at low speeds.
Again I caution against NOT using the anti-torque tool.......and do not tighten things with a big grunt, such that the fork is at full left or full right mechanical stop whilst doing that tightening. It is possible to twist the forks out of alignment!
7. Assuming you don't need bearings & races, NOW is the time to, and you MUST!!; tighten the lower fork triple clamp allen bolts (don't even think of forgetting this step!), and to do a thorough check-over, to be sure you have assembled everything and tightened everything, except assembling the hydraulic damper, instrument pod and gas tank.
8. Assemble damper, pod, gas tank. Again check that all looks OK, no cables interfere with steering, etc.
9. If you have a fairing & are assembling the hydraulic damper, with those pesky wire clip keepers, you will need patience & likely a small inspection mirror. Grease those ball ends before assembling the damper. Put a tiny amount of contact cleaner or silicon spray onto the instrument pod electrical plug contacts, & don't forget the screw that holds that plug in place (and do not over-tighten it).
10. AGAIN, recheck all those bolts, screws, etc. You DID tighten the lower triple clamps? Fork tops? Did not get any cables crossed over or in such a position that the steering is not free???
11. The rear swing arm must be adjusted correctly. If not, the motorcycle will not behave properly during your test ride.
Two types of swing arm pivot pins are in use. The very early pins were 48 mm long; the wrench needed is 6 mm hex up to production of 09/1980. Thereafter they are 42.5 mm long. The thread has always been 20 x 1.5 mm. Both types will interchange.
To adjust the swing arm, first insert the pivot pins (if not already), & tighten very lightly with an allen wrench (NOT a torque wrench). Go back & forth between left & right pivot pins until the spacing from the swing arm to frame is approximately the same, as seen with your eyeball, or using a drill shank or small allen wrench as thickness gauges. Approximate is OK for this first step. This approximately centers the swing arm in the frame. Install the locknuts (if not already) on the pins with your fingers or the modified 27 mm or modified 1-1/16" socket (see below on the socket modification. The nut, at this point, should NOT be tightened, but maybe a couple turns loose.
Torque ONE side pivot pin allen (hex hole) clockwise to 15 ftlbs. Back off from the 15 setting ~ half a turn, then re-torque IN clockwise movement (only) to 7-1/2 ftlbs.
Check the spacing from frame to swing arm. See if it is the same, left and right. If not, back off one pivot pin & tighten the other. Remember, clockwise movement during the tightening to 7-1/2 ftlbs. When the spacing is the same, then tighten ONE of the locknuts to 72 ftlbs of torque. Recheck the spacing. If still OK, then torque the other side's nut to 72 ftlbs. If the pivot pin and nut threads are in good condition, the tightening of this fine threaded nut will NOT cause the pivot pin to rotate during the 72 ftlb torqueing. If you are worried about that, put a mark on the pivot pin face and associated frame opening, so you can see if the pivot pin moved after you tightened the nut.
The final step is to force grease into the hex holes with a rubber tipped grease gun. I prefer to force enough into the bearing, and out into the area between frame and swing arm, to be able to smooth it into a ring of grease, with my finger tip. This will keep water and dirt out of the bearing. Grease the same way every now and then.
socket: You can use a 27 mm or 1-1/16" socket. The
socket MUST be modified by grinding the END FLAT AND SQUARE, enough so there
is no taper on the inside, as the 27 mm nut is thin
and you do NOT want to damage the nut.
Grind the OUTside of the socket, and do this squarely,
where it fits into the swing arm cavity...
so that the socket goes past
internal projections & then
over the 27 mm nut completely &
thoroughly. To explain this further, SOME bikes have a second
circular "ridge" inside the swing arm cavity hole, so the socket must be ground on the outside. The very nicest way to modify the socket is
to chuck it in a three jaw chuck on a lathe & do the end &
side of the socket. The entire job
can be done very neatly on a lathe in 5 minutes. The OUTSIDE
diameter of the end of the socket can be
done on any grinding wheel if you do not have access to
a lathe, but the END must be done fairly
precisely, so it is FLAT....a belt sander will do if you are
careful. You can also purchase one of these modified sockets from a couple of aftermarket BMW tools suppliers.
12. Inflate tires properly. Remove saddlebags, and any rear trunk if not too much a bother.
13. Road test without passenger (passenger weight can modify the effects you are going to be looking for). Saddlebags, top boxes, & fairings/windscreens for that matter, have a noticeable effect on high speed 'weaving', rather noticeable on downhill sweepers at around 85 mph. This high speed weaving is NOT the weaving we will be trying to adjust out!...which is low speed weaving, as it is normally thought of.
The first road test is for low speed weaving. Do this on a flat road, not uphill or downhill. For ALL these road tests, ANY damper MUST be turned off! You will likely want to do this test at about 20-30 mph. Do NOT do it at 50+. If your steering bearing adjustment is too tight, you will find the steering a bit heavy, a tendency to weave & not track smoothly, particularly in turns. If you have this condition, remove the gas tank to protect it, loosen the top capnut (use the anti-torque tool!). Loosen the adjuster nut a small amount, perhaps a few degrees. Retighten the top cap (use the anti-torque tool!), put on the tank, do another test. You do not have to loosen & then re-tighten the lower triple clamp bolts unless you make nearly a full flat adjustment change; which should be unlikely. A full flat means 60 degrees here. If you DO loosen the lower triple clamp bolts in order to make a top adjustment, be absolutely sure you retighten them before you go riding!
If things feel correct in the 20-30mph range, try removing hands from the bars and giving the bars a small hit one way or the other, at about 35 mph. Any tendency for an INcreasing oscillation is cause for investigating tire balance, tire condition, even wheel bearings, etc. Any slight oscillation (also called a wobble) should be damped out instantly with the hands back on the bars. If not, you have a problem to look into.
High Speed tests:
I have almost never seen an un-faired, no-windshield Airhead with properly adjusted steering head have ANY problem at high speeds. However, it is possible, & things like large bar-mounted windscreens; bad tires, poor wheel bearings, etc., can cause problems. The worst case might be loose steering head bearings and a short wheelbase /5, with a bars-mounted windshield or bars-mounted fairing.
15. High speed tests are usually done by beginning at around 40mph and increasing in increments of testing up to about 90. Every 10 mph, take hands off bars and tap them a tad, which causes the bike to turn a bit, and check stability.
16. Airheads, particularly the old ones with two sided swing arms, may have an effect called, among other names, Rubber Cow, Gummikuh, or a hinged-in-the-middle feeling. This effect is a weaving feeling, often a nasty one on the RS & RT models with bags & especially with a large backrest/tour trunk at around 80 mph+ in downhill sweeping turns. This effect is primarily caused by wind effects on those accessories, and the not very stiff rear suspension & the frame design, particularly the rear sub-frame. BMW improved this with the single sided swing arm and elimination of the earlier style of rear sub-frame, & further improvement is possible with better shocks, springs, & modifications to stiffen the frame (the modifications of welding tubes to the swing arm generally have only a small effect). Surprisingly, a good front fork brace can help a bit. So can, especially, a thick top triple plate. Aftermarket top triple plates are available. Some have modified lower triple's for this, some have doubled up on the top plate; those are not as pretty. If your bike exhibits this uncomfortable weaving at HIGH speed, particularly in downhill turns, it is likely not the steering head adjustment! NOTE that a stiff aftermarket TOP triple clamp plate will help much more than a fork brace (which are often not properly installed & CAUSE problems with stiction).
17. It is FAR better to have the forks very slightly too tight at the adjuster nut, putting up with very slight low speed weaving, than too loose. The reason is that if too loose you MAY have a chance of a high speed wobble. This statement is worth extra notice on the SWB /5 bikes. Once you have done this procedure & have the steering adjusted correctly, you likely will get it correct the next time without having to do these road tests. I suggest you check the steering adjustment, now that the bike road tests perfectly, by having the front tire off the ground, & nudging the steering each way, & thereby see, for YOUR bike, just how much friction & movement occurs. The next time you do your steering bearing service, simply adjust for this same effect!
Notes, addendum, etc:
A word of caution here about high speed diverging fork oscillations/wobbles. Due to gyroscopic and other effects, these forces at speed are fairly high. If a serious wobble begins, & forceful hands-on-bars pressure does not diminish or eliminate the wobble, you may well have a SPECTACULAR accident. If you have adjusted your fork steering head bearings correctly, any induced oscillation from the steering head bearings will be dampened easily. If your tires are road crowned, under inflated, way out of balance, etc., you can still have an oscillation problem. PLEASE DO NOT DO HIGH SPEED TESTS ON A MOTORCYCLE WITH A WORN REAR TIRE SUCH THAT THE CENTER OF THAT TIRE IS SHAPED RATHER FLAT, AS OPPOSED TO SOMEWHAT ROUNDED.
Approach road tests carefully, deliberately, in stages, slowly increase the speed from one test to the next test. Do not suddenly jump from a 40 mph test speed to 80 mph.
I have sometimes been asked if the steering head bearings have an official preload adjustment specification. YES, they do. The factory uses a tool that allows a torque wrench to be applied to the steering head top nut area. The factory specification is, believe it or not, different for the drum and disc brake models!! I have some ideas on why that is, but no proof. Be my guest in trying to figure out why there are two specifications.
For the drum brake front ends, the steering head is to be at 1.9 +-0.2 footpounds. For the single or dual disc brake front ends, the steering head is to be at 2.6 +-0.14 footpounds. Obviously you are not going to use a foot-pound wrench, they are just not accurate at such low values. ****There is also other literature from BMW that states that the steering head, without specifying model differences, should be at 30 +- 2 INCH-pounds. I am OK with this, same as I am with the above values. I think that if you use MY methods which involve the nudging of the bars and the road tests, that you will be closer than factory setup, and, your bike will handle much better! BMW's own Service Manual specifies how to set this torque. You already know that the top cap nut must be set to its torque setting, as tightening it changes the bearing preload CONSIDERABLY. The Service Manual says to place a stop of some sort between the left lower triple clamp and the steering head, such as to limit the steering angle to 20° to the left. You attach your adaptor wrench or socket to the center acorn top cap, yes, that 36 mm top cap (and I will tell you that it works fine with the later 41 mm one too). The torque you apply must be to the center of the top nut (acorn nut or other). The cables and wiring must not interfere with the readings. The proper torque to move the forks from that 20° left to the center-ahead position is 30 INCHpounds. I don't know anyone that does this sort of thing by a torque wrench, but you might want to. You STILL must/should do the slight hit on the bars end test, and, of course, the road test.
It IS possible to modify the dogbone wrench to enable an inch-pound or other more sensitive wrench to be used. I have tried using a torque wrench, and it does work out OK, but not nearly as good as with road testing & adjustment from those road tests. I also have found that since the cables are almost certainly not going to be disconnected, nor wiring disconnected, they all have an effect on the steering, so that about 4 ftlbs was about correct in many instances....but the road test is the way to prove what YOUR bike needs. Just HOW MUCH drag you should set the steering bearing preload for, is, therefore, a good question. Generally, the drag is set rather HIGH for sidecar use. As I have mentioned in this article, for road use by a RS or RT, probably just a wee bit tighter than just allows the fork to not quite fall to one side, when nudged. An ST, G/S, S, and many other Airheads...and K bikes....are set so the forks will JUST fall to one side if nudged.
The procedures in this long article have been abbreviated in places & expanded in others. If you follow them, make notes for your own particular machine. The differences between Airhead models and years is mostly adjustment parts. Yes, there are variances in washers, nuts, adjustments, split ring...etc....but the basics & what you want to end up with, are the same. Steering head bearing and lubrication should be done every 30K or so....OR, when you feel center notchiness. BEST to do it BEFORE such notchiness is felt. Non-faired models ridden in wet weather may find the need to do this more often, hence the reason I selected a long life grease having great resistance to water. Having steering head set much too loose will almost surely cause bearing damage and lousy handling.
1. I did extensive rework of the /5 forks decades ago. TWO modifications are going to make the dampening stiffer...in both directions. You can braze up one or two of the rod holes, and you can change the damper orifice to 15.5 mm, which is 31-42-234-506. In BMW's parts books, you will find the damper ring that is available in a heavier damping version to be called the 'more stringent' version.
The headlight fork tube ears,
at the top, just under the top triple clamp, have rubber bushings...a
sort of rubber O-ring. FOUR sizes were made!..you need to use the one that fits properly on
31-42-1-232-527 is 3 mm thick
31-42-1-230-696 is 4 mm thick
31-42-1-230-697 is 5 mm thick
31-42-1-230-698 is 6 mm thick
There is also a rubber bushing or O-ring, located at the BOTTOM of the headlight ears. That one is only of ONE type and part number: 31-42-2-000-385.
3. Springs: The BMW heavy duty springs are OK. I prefer them to the Progressive BRAND of springs.I like best the Hyper-Pro progressively-wound springs.
11-24-2006: edit gaiters
01-10-2007: add information on oil viscosity for Mil 5606 04/15/2009: clarify details on gaiters
12/07/2009: Clean up appearance; add the stiction section from the steering.htm article
03/02/2010: add a couple of hyperlinks and clean up verbiage a bit.
07/02/2010: Combine with old Steering.htm article, 100% revise and add images.
07/03/2010: Finish above.
FROM 02/02/2011: Begin going through entire article, to update, do clarifications and other editing, move things about for additional clarity, and add a separate section at the end for HINTS.
02/08/2011: finish preliminary work, and include the new Miscellaneous section
08/28/2011: minor clarifications 01/07/2012: Clarify the damper rings information and fix the typo where I listed both the -506 numbers in the beginning.
01/31/2012: Small changes in area of 1991+ adjustments recommendations
04/09/2012: add some Rancho Shocks gator numbers
08/08/2012: Re-number from 54-10 to 54-10A, due to addition of section 10B on oil filling amounts. MOVE section on types of oils to 54-10B. Remove note 1 in miscellaneous section, moving it into 54-10B. De-number the section. Clean up article.
03/29/2013: Edit item #11 (in Reassembly and Adjustment section), for clarity and additional details.
04/08/2013: Add browsers notes.
04/17/2013: Add section on bearing replacement.
06/17/2013: Add first section on the description of the 1981-1984 forks, add the sketch, notes, etc.
11/28/2013: Update bearing description information, and sources. 04/11/2014: Add section NOTE on disconnecting electronics and battery for stick welder use
09/26/2014: Clean up article, moving things about, make article better for smaller screens, etc.
05/05/2015: Fix hyperlinks
05/17/2015: Re-arrange Stiction/braces/etc., portion.
10/25/2015: Re-arrange article again, shorten it, make it more succinct where I can, clarify some details. Add links.
12/01/2015: Add working hyperlink to Randy Glass' article on Duane's website. Fix meta-codes, etc.
02/26/2016: Completely rework the article. Justify left all text, photos, & eliminate wrapping of text at photos. Change H. Lines. Update meta-codes, including adding Viewport code for small device viewing........ETC.
02/26/2016: Again completely re-work entire article. Increase font size. Reduce colors and use of them. Justify photos to left. Change horizontal lines back to 100%. Eliminate hard breaks throughout. Add viewport code to meta's. Most of this work was done to have the article display better on small screens, such as Smart Phones.
04/24/2016: Minor cleanup, metacodes, typos, grammar, spacings, hypen-space stuff. Finish left justification things.
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Last check or edit: Tuesday, May 24, 2016