Adjustment of clutch levers; replacing bushing in bars lever.
Fixing potential cable breakage...& new cable problems.
Lubrication of clutch splines (input splines of transmission).
Preventing broken ears at transmission clutch lever.
Clutch carrier/flywheel, bolts, crankshaft end play.
Throw-out bearing & pushrod.
Crankshaft end play spacers.
1981 Clutch/carrier problems.
Copyright, 2014, R. Fleischer
Article 60, subsection 9
Under NO circumstances should the flywheel or clutch carrier, on ANY models be removed without FIRST blocking the crankshaft! http://bmwmotorcycletech.info/flywheelremovalwarning.htm
You MUST block the crankshaft!!! DO NOT TAKE A CHANCE!
Many HAVE removed & replaced an Airhead flywheel or clutch carrier without blocking the crankshaft with no problems. My advice,
VERY strongly given here, is to take a minor amount of time & make & use at least my simple crankshaft
blocking tool. If you do not use some sort of
crankshaft blocking tool, & your
crankshaft should happen to move forward enough (does
not take much pressure
nor does it have to move far!) to have one or both of the thrust washers
fall off their pins,
you can cause VERY serious damage as you attach & bolt-up the flywheel
clutch carrier. At a minimum, if the forward thrust washer drops, you may be
to get it back on its pins without a LOT of work. Do NOT take a chance!
Since it is a MUST, in MY OPINION, to mechanically block the crankshaft from moving forward at any time during the process of removing/replacing a flywheel (or clutch carrier as it is called on 1981+ including some 1980 models), you need to know how to best do that.
This can be done in several ways. I recommend you do NOT use 'a towel' between the front cover & the alternator rotor, as is sometimes done. I recommend a simple & neat method...just make a tool out of a piece of Allen wrench material, weld a disc (fender washer) on one end, making the length such that the Allen end fits into the alternator bolt, & the disc end presses against the inside of the outer timing chest cover. Usually 3/4 inch overall. The length should be such that there WILL BE some light pressure applied by the cover to the tool, the cover being screwed back towards the engine lightly (but not touching the engine case, ...again, LIGHT screws pressure). The tool should be just long enough that the cover CAN NOT fit fully home all the way. Obviously you don't want to tighten the outer cover very much & DO NOT NEED TO!
A further treatment of how to make this tool, & a photo of it, is in the http://bmwmotorcycletech.info/tools.htm article on THIS website, item #8A. Note that making the tool requires a very small amount of welding. If you do not have a welder, or do not wish to have the tool made that way, you can just use a piece of allen wrench; OR, simply remove the rotor bolt & use a common bolt temporarily at the rotor, adjusting its depth to fit the outer cover (with precautions on the bolt rotating if you rotate the flywheel). That above tools article also has photos of the clutch disassembly & assembly tools...you may need one or more if you have an early model. There is another place on this website with a photo, etc., of that tool...and another 'tool'. I suggest you go look at that article, NOW: http://bmwmotorcycletech.info/flywheelremovalwarning.htm >>>>SEE and READ IT!!!<<<<
Be sure the OT mark is in the timing window when removing & replacing the flywheel (or clutch carrier). Do this "removing & replacing" ONLY when the pistons are fully extended outwards. When the flywheel shows the OT mark in the timing hole, both pistons will automatically be fully extended outward if the flywheel or clutch carrier was already installed properly. If that is not seen, then the flywheel is mounted to the wrong crankshaft bolt holes. Many a person has made this mistake! The flywheel is not 'indexed' & can be installed to the wrong crankshaft holes. The flywheel is also to be centered in the proper selected holes, by moving it back & forth very slightly CW-CCW in its holes, before being fully tightened. It may be moveable a TINY amount if the bolts are a fraction of a turn loose...so find the centering position, then tighten carefully, & then torque to specifications.
Clutch parts, including flywheel or carrier, should be identified by marking with paint or punch pricks before you disassemble. BMW did that on some models. If you see factory marks, those marks are to be oriented so they are, as best possible, 120° apart to each other; that is, they are NOT lined up! BMW marks may exist & may not. This is contrary to what the repair industry usually does, which is to align marks. I use one punch prick opposite another for the first marking; the next set, if needed, is two punch pricks, then three, etc. Arrows also work. Those are standard methods. I don't use paint or other marking methods.
/5 clutches had changes during production.
The replacement diaphragm springs
were changed, & the 6 spacers were no longer used.
Spacers are sometimes added if parts have been resurfaced and are thus thinner.
There were several types of diaphragm springs used, & the heavy duty type is usually stamped with the part number. That part was 21-21-1-234-035. Some call that the 'sport plate'...but it is the diaphragm spring.
There was a spring common to the R90/6 and R90S, 21-21-1-231-842; it is obsolete, NLA.
The pressure ring was updated, that is part of the spacer deletion mentioned above, & the new pressure ring is more rugged, & a better heat sink. If you are updating, the updated parts are the -035 spring; the 21-21-1-236-332 clutch plate which has an extra set of rivets & a plate, on opposite side, locks those.
Another later part to use is the 21-21-1-231-666 pressure ring. The early pressure ring had standard blade screws which should not be used; instead use 6 point head Allen screws; torque to a target of 16.6 foot-pounds.
BMW made major changes to the clutch/flywheel parts between 1980-1981.
The "flywheel" was eliminated, & a lighter 'clutch carrier'
was used. The throwout
bearing was also changed in design. These new parts are very different from earlier models. The new clutch assembly is lighter &
requires much less force at the handlebar lever; but
engine vibration generally
increased due to the lighter flywheel effect.
Clutch friction discs were asbestos-containing material in the old days, which had, I THINK, a better Coefficient of Friction, than today's replacement discs; probably another good reason to use a sport diaphragm.
New discs are ~6 mm thick. When worn below the official limit, 4.5 mm, they
may slip. Slipping
to show up first when using large amounts of power
in top gear. If the rest of
parts are in reasonable condition
slippage may not occur until ~3.5 mm. No hard
& fast rule here,
due to wear
(cupping on the pressure plate, wear on the diaphragm, friction material, etc.
I check clutch parts on a machinist's flat, but you can use a flat piece of glass, etc. I use feeler gauges and other methods to determine the dishing, etc. Check disc thickness via vernier caliper or micrometer. Another way, very commonly done to determine if the parts (besides the friction disc) may need resurfacing or replacement, is to measure the width of the worn disc of the friction material (both sides together), near the outside edge, & near the center. If thickness is considerably different, then all the friction parts of the clutch need attention. While there is no directly official specification, you could determine it from how BMW shows the various distances, etc... and find that to be ~0.3mm...disregard that, and use my ~0.5 mm. Check the diaphragm spring with vernier for height, etc. See the specifications in the various literature. The diaphragm spring has specifications, vary with model as to height & as-fitted pressure & when pressed flat. There is also a specification for the height differences of the spring fingers. Ask about these on the Airheads LIST. I suggest that only the un-pressured height usually needs be checked (besides inspecting for unusual wear).
If you replace just a friction disc & the mating parts are worn enough (especially if they are not flat or flat enough) the clutch may slip...although if used gently, the clutch may break-in after a few hundred miles & then be OK. Using gently here means not letting the clutch slip much, which will happen if you use high throttle and top gear until broken-in. Professional mechanics usually do a clutch job by replacing the three $$$ parts, but you CAN just replace the disc, but I would recommend checking the taper/flatness of the parts. The heavy duty higher pressure spring is a good idea, especially with these later non-asbestos discs on the early clutches.
Clutch PARTS can be overhauled. Southland Clutch modifies old parts & supplies a thicker disc (as needed with their machining of the originals, etc. http://bmwmotorcycletech.info/references.htm under C for clutch....or, see much later in this article, below, for their information.
Disassembling the clutch:
Clutch bolts on early clutches (NON-clutch carrier types) are not long enough to remove them without a spring-loaded problem from the clutch. It is important to unfasten the early clutch bolts evenly, in a criss-cross fashion. So, how to do it? You FIRST remove three, alternately spaced, of the six. In place of those three, you install three longer bolts & spacers from the hardware store....unless you have the BMW factory-type clutch tools; or, tools from some aftermarket maker. Using either the hardware store bolt method or the factory or aftermarket tools, you can now undo the other bolts, evenly, in a criss-cross pattern, bit by bit. I reuse the early models bolts (I inspect them of course).
On the 1981+ clutches (clutch carrier type of clutch), you will be using new bolts. Use NEW special vibration-proof washers too! On the 1981+ clutches, there is NO need for the use of special bolts or tools, you simply remove the original bolts. Note that these clutches can stick from corrosion at the bolting areas. Use a small flat blade tool, even a screwdriver; gently pry a bit here, a bit there, & over a few minutes the clutch will come apart. Here is a photo of the factory-type tools for the early clutch (including the centering tool): http://bmwmotorcycletech.info/ClutchFlywheelTools.jpg
A SI was issued with a lot more information on where to
grease the mating clutch parts ...ETC.
That is in the 1992 service fiche, page 4, G13/H13/I13. Basically, it is the
contact points of
the diaphragm spring. I use a moly grease there, very sparingly.
HINTS: Exceptionally stiff clutch action can be due to a BAD CABLE; or, worn, grungy or failing bearing & even broken parts in the clutch throwout bearing area, including the bearing, piston, etc. Do NOT fail to change the clutch cable if bad; it can FEEL OK with the cable disconnected at the transmission end, yet be very stiff when in actual operation. Do NOT install the clutch cable running with sharp bends; nor have more than the ONE tie on the right down-tube. Be SURE to grease the bar lever clutch cable barrel-end & barrel itself area (moly!). Be SURE that the cable inner strands are NOT fouled by the slot in the bar lever as you pull the lever back towards the bars or move the lever up and down. Yes, that means to ALSO wiggle the lever angularly UP AND DOWN, to see if there is so much play in the lever bushing (nylon & replaceable) that some strands foul in the lever slot. It is especially important that the cable end, including its cable barrel, be free to rotate in the clutch lever. The crimped area at the barrel end must not foul the lever either, & you might have to file that a bit. Pulling the clutch lever slowly backwards will show by #1 eyeball if the barrel is moving freely. If not, unfasten the cable from the lever, & clean up any rough spots on the barrel, then re-reinstall, again using a moly grease on the barrel.
Some clutch cables are poorly made. There have been poorly made cable ends sold by BMW...so do check the clutch cable ends very carefully for appearance and that operation in the lever is proper.
If the lever nylon bushing needs replacement, do so. If that bushing wears too much, the lever will angularly cut the cable. Heat the lever if the new bushing does not push right in. If the new bushing does not fit the pin properly, then ream it SLIGHTLY. Don't own a tapered 8 mm ream? You can use progressively larger (by a thousandth or three) drill bits...just do NOT remove too much material! There is a waverly washer used in a machined depression in the clutch lever, it must be there.
curved area for the barrel (at the lever at the rear of the transmission) may need filing to
enlarge the curve very slightly, so the barrel will easily rotate. That is VERY common.
More on that in next paragraph.
More information on cables and levers, etc: http://bmwmotorcycletech.info/controlcables.htm
Clutch cables...and transmission lever (more):
BMW clutch cables (since just after the earliest /5 bikes as originally shipped) are lined with a plastic material. DO NOT LUBRICATE. BMW has sometimes shipped cables with POOR QUALITY cable ends, you may have to file the barrels round or otherwise fix the ends. While I have discussed the barrel on the clutch cable which fits the handlebar lever, and the curve in the transmission lever for the clutch cable barrel, here it is in more detail. This problem is due to rough manufacture of the clutch cable barrel (at the transmission lever end of the cable); and/or, poor machining of the clutch actuating arm located at the rear of the transmission. The fix is easy ...and lasting. I always check this area when I am either adjusting the clutch... & when removing the transmission for any reason.
1. Inspect the cable barrel. It must be smooth & round. If not, file it so, finishing with fine sandpaper. Be sure that this cable barrel can rotate smoothly in the clutch lever fork. If not, using very fine sandpaper, or? polish the rotating area & very slightly enlarge the opening in the lever, so the half-round area is a bit bigger. I give a slight bias to the main body of the lever, rather than the tip. Clean up any sharp edges; & then use fine sandpaper on any convenient round object, such as a screwdriver shank, to smooth the area. Having a lever and barrel that work smoothly together will greatly extend clutch cable life.
2. Clean up the lever slot with sandpaper, so there are no sharp edges. This ensures that even if the nylon bushing in the lever wears considerably, the cable inner strands will not excessively rub the original sharp-edged lever slot.
4. CHECK how the cable barrel rotates, in the arm, it must rotate smoothly. Lubricate it with moly grease.
Throwout bearing, etc:
Slipping clutch? STIFF or no clutch or slipping...when engine fully heated up (or even when cold)?
This problem originally was reported now and then with motorcycles as late as the early 1990's manufacture! It is NOW clear that the problem exists, even if rarely, on the last of the Airheads, such as the R100R, & even with the "new" throwout bearing that BMW went to. THUS, this section was revised 05/16/2013; and minor changes in 2016.
On 1980/1981 & later models, the PLASTIC (which looks like aluminum) or
ALUMINUM 'piston' (yes,
both types were made) with the metal center, that the
clutch lever at the back of the transmission applies
its force to, might be too large
in diameter & stick in the transmission bore
when the transmission is hot. This
piston is located next
to the 1 inch mark of the ruler in the photo well-below. The LIMIT is 28.7 mm, & it
be sanded down, or replaced. Tom Cutter has reported that BMW has made
updated throwout bearings, see the -167 number quite a few paragraphs below, that
were both good, AND BAD. The original problem occurred because of accumulated
tolerances on some
transmissions throw-out area bore sizes, & similarly with these throw-out
pistons. I believe that the plastic
ones ALSO MAY age, expanding over
time/miles. If the piston fits into the bore a bit too tightly .... & it may still
fine when cold, then, under some circumstances, PARTICULARLY when HOT,
the piston may
stick. That is because the piston material expands very
considerably faster than the aluminum
bore it fits into. Obviously this means
that the BEST check is with a hot transmission.
The problem can manifest itself in several ways, INcluding a hung-up or very stiff operating clutch, or a slipping clutch. Measure the piston, & if it is over 1.13" (28.7 mm) when hot, you may want to reduce the outside diameter a bit. I have seen these as large as about 1.142" that still worked OK (NOT all at that diameter WILL be OK!!). It depends on the transmission bore hole, but you won't be changing that. You may be better off with modifying your original piston, rather than take a chance on BMW's 'new' piston....granted it is now a one-piece assembly. I just do not see any big advantage to the new design.
As a general rule, it appears that if the piston has a diameter of 1.122" (28.5); it will work in all the transmissions.
I can't give a hard & fast rule here, but if your throw-out piston is up to 1.141 or so, I would certainly see how it fits, & if a bit too much friction with a HOT PISTON, I would recommend sanding the OD a bit; keeping it concentric! You might want to check the fit, hot, if you have any hot clutch slipping problems or any stiffening or hung clutch problems, but OK when cold. There have been some reports that the plastic piston expansion can happen & then be more or less permanent; after years of seemingly being OK. I think the 'permanent' expansion, if that happens, is likely to be occurring almost from brand-new, & that it might take a very long time & many miles, for the expansion to reach the grabbing-seizing point. NO PROOF OF THAT.
BMW has had several versions of the throw-out parts, & offers a
23-13-1-464-167, which is another way, if somewhat
costly, of coping with a sticky hot
piston. If your old bearing is quite bad,
& piston sticking when hot.....you could consider
this part, as it is a new
design, incorporating the bearing, & it supposedly has the proper
If your old items are in good condition, you really do NOT have
to spend the money, ....you can sand your piston outside diameter. It has
been said that there is a
special surface coating on the piston, & sanding
or otherwise machining is a bad idea...NOT TRUE, sanding works fine, &
lasts. Just do NOT remove way too much material,
or the piston could
cant sideways. It is VERY UNLIKELY you will remove too much material.
NOTE that new-style (-167) pistons have been reported as expanding & sticking! I had TWO reports that a new-style piston expanded slightly & permanently, & also gave clutch problems with the transmission being COLD. I personally have not seen this (yet)....& probably will not, since I have stopped doing work for others. It has separately been reported to me that BMW MAY have recently shipped all-plastic parts that have the same old problems!
It was reported in May 2013 that a R100R with original "new type" piston assembly was seizing, & was repaired by slightly reducing the piston diameter. That was the first instance I had heard of this on a R100R. The R100R was the last version of the Airheads, produced into 1996. Even in 2016, there are reports of piston sticking with the new -167 piston.
It appears that BMW has made the -167 piston assembly in TWO diameters, and only the smaller one works well.....so, if yours is new, and over 28.5 mm, I suggest you sand it down and then see how it fits!
|At this point, I think it appropriate to caution that if your clutch operation becomes faulty in some way after the engine is fully heated-up, the throwout bearing & piston unit should be checked to see if it fits OK cold; &, again when the engine and transmission is quite hot from a reasonably long ride, perhaps 20 miles.
If the clutch is not properly adjusted, usually indicated by no free play, hot or cold, at the bar lever, the throwout bearing will WEAR OUT RAPIDLY. Best clutch operation is had with proper adjustments, at the transmission clutch lever & the bars & is outlined in this article.
My described modification can be done on a lathe with some sanding paper, & you can hold onto both ends of the piston; you can also chuck the rather short shaft tip end in a drill press & use some rather fine sandpaper for the job; which takes a few minutes. The drill press chuck won't grab strongly on that very short tip, so don't over pressure with sandpaper, &, take your time. The sandpaper & throwout unit should be DRY, NOT lubricated, during the sanding. Use a micrometer or vernier caliper to first measure the piston diameter, & repeated measurements as you sand it down, which happens very slowly. Use a moderate speed of rotation. I usually just do this, rather than replace the assembly...as there have been problems with the new type, and it takes me only minutes to sand the original. A shop probably would not sand the old part, but replace it with the updated part. I am not convinced the new part is perfect.
Inspect the bearing & if it looks bad, replace it. Grease it with a good thin petroleum grease (Do NOT use moly). While the bearing is theoretically ultimately lubricated by oil from the transmission, that does NOT happen for some miles after initial assembly.
NOTE that these bearings, whether ball type, or needles type, can fail, and MOST of the time the failure is NOT due to what you might think (although the bearing will be damaged, if not lubricated upon installation). The problem is that the transmission oil became contaminated by moisture. Transmission oil is moisture contaminated due to any combination of the following factors:
Leaking speedometer cable boot at the right rear top area.
Water hose has forced water into transmission via the hollow bolt.
VERY rarely it comes from water in the bottom of the air cleaner area, where a 13 mm (head) bolt screws into the transmission. Contrary to old BMW recommendations, I suggest gooping the bolt threads, even under the bolt head (washer too), with a LIGHT amount of Permatex NON-PERMANENT Form-a-Gasket.
The 4 speed transmission had a balls type throw-out bearing; the 5 speed transmission (1974+) had a radial needle bearing type; in 9/1980 BMW went back to a ball bearing, of a new design. Can you figure out why a radial needle bearing is a poor design (but CAN work adequately), as far as pure engineering is concerned?....think, then read the next paragraph.
((( thinking time...thinking time....1, 2, 3, )))
The radial needle bearing for a throwout bearing in an Airhead is a POOR design, but works fine most of the time. When RADIAL needle bearings, that are equal in size from end to end, are pressured (say, by a flat plate) & rotated circularly, the needles try to rotate at the same speed at BOTH ENDS of each needle....that is, from end to end of each individual needle. This is NOT POSSIBLE, if you think about it, so they scrape around....forcing any grease or oil out. BUT, the bearings are NOT being constantly rotated, only when the clutch is used, & when the transmission oil hopefully lubricates the bearing. Thus, the bearing does hold up OK most of the time. See downwards a couple of paragraphs, for exceptions. If the grease or transmission oil is not there, & a little moisture condenses there, or excessive clutch hold-in times are often used; and/or combinations of these things INCLUDING OLD OIL.....the bearing can start to deplete its lubrication, & actually freeze up. That is more likely for dirt riders who use the clutch to control speed. When you install the bearing, you lube it with a thin grease (NEVER a moly grease), & that grease will lubricate the bearing until the transmission oil gets to it enough, & washes that petroleum grease away.
NOTE: The 4 speed transmission & the early 5 speed transmission clutch push rods had felts located in a pushrod groove, & are best installed from the front. Later ones must not be installed from the front. More to all this, below.
Below is a picture of a 1982 felt-less clutch rod, the superior type ball bearing, piston with plastic outer, the internal spring, a new rubber accordion cup, and the band-clamp. The rod is about 9 inches long; the piston cup is about 17/32" wide on the DARK plastic portion.
The bearing is lubricated with transmission oil during operation;
but that takes
time & miles after the greased throwout bearing is installed. I
always use a very
light NON-moly grease when installing this bearing. The
"felt-less' clutch rods came in 1981.
Prior models of clutch rod had
23-21-1-230-440, which is best installed on the rod, & the rod inserted
FRONT of the transmission. It is possible from the rear, with a homemade
tool, but I recommend against it.
The felt IS necessary on models prior to 1981, otherwise the clutch can become oiled; thereby slip, & be ruined eventually.
1981 & later models have a lipped seal at the rear cover, 23-12-1-243-522 not easily replaced....the transmission must come apart. Install
the pushrod, oiled, FROM THE
REAR, rotating it a bit to avoid damaging the seal
(which you will, if you
install from the front like on earlier transmissions).
WARNINGS about the clutch arm:
Earliest models, the /5 that is, had the clutch actuating arm at the rear of the transmission held to the transmission via a cotter key. Very reliable. Later, but still rather early models, had the clutch actuating lever held to the two tower bosses of the transmission cover by a PIN that used a single clip. That C-clip fit on the pin in a groove in the pin, at the INside of the lower tower boss. If the C-clip came loose, the pin could come upwards out of the lower boss. The next clutch application often broke off the lower transmission boss ear...necessitating a transmission overhaul....or some inert gas welding at a minimum for a permanent fix (temporary fixes are of several types, not treated here). Usually the breakage happened while you were shifting, going down the road; and did not happen in your garage...and the ear was lost...so it now was more complicated to get back on the road. Replacing a rear cover means re-shimming the transmission; so you might as well overhaul it. Fixing the problem before it can happen, costs VERY LITTLE, & can save
you a HUGE amount of money...not to mention headaches, or being stranded.
The PRE-PROBLEM FIX:
Remove the old pin & clip & install #23-13-1-241-484 pin that has a flange, & won't fly out. This is used with a clip that is part number 51-23-1-864-963. It is also possible to use a bolt & a self-locking nut; I suggest a shoulder type bolt, & do NOT try to squeeze together the ears, they will break! Tighten the nut JUST enough so the bolt has some free-play & is NOT squeezing the transmission cover ears!
LUBRICATE the parts, no matter the type of fix, with moly-grease, during assembly. This is an excellent time to clean and lubricate the clutch arm.
BMW had a Service Information bulletin (we call them SI's), November 1991, #11-049-91, sub number 2495, this can also be seen on the 12/92 fiche on page 3, G23. Basically, it stated that while the flywheel bolts were previously at ~75 foot-pounds (100 Nm), they were now to be at 90 foot-pounds (125 Nm), cleaned threads, & then the threads were to be OILED! BMW specifically said that the bolt limits would NOT reach their limit of elasticity at that torque, and could be REUSED! I will NOT tighten them that tight. Makes me very nervous! However, some do tighten them that tight, & I have heard of no problems reported. It is YOUR CHOICE. NOTE also that this is in regards to the 11 mm bolts, & applies to 1981+ models....certainly not the smaller /5 and early /6 10 mm bolts; which need replacement upon each use, which the 11 mm do not. The 10 mm bolts in the /5 & early /6, are absolutely NOT to be torqued to such high values.
There have been a lot of different specifications on flywheel bolts over the years. There were two lengths of 10 mm bolts used. I use, clean & dry, torques of 42-45 foot-pounds on the 1973 & earlier engines; for the 1974 I use 52-55 ftlbs; for 1975 & later up to the 1981 models, I use about 75 to 80 ftlbs. I use about 80 ftlbs, clean & dry threads, on 1981+. I am OK with that value even if faintly oily.
Grabby clutch: If your clutch is grabby, it can be due to a number of causes.
the transmission input shaft splines be regularly lubricated.
get dry, the shifting is stiff,
poor, and may be somewhat difficult to get from 2nd gear down to 1st gear, or just to engage 1st.
While you could put a
FAINT coating of a DRY type moly on the disc splines, I generally recommend you
do not, as I worry you will over lubricate the disc. So, I usually say: Never lube
the disc spline, just the transmission
INPUT spline (for that you must use a moly grease). Cleaning & re-lubrication
be done at a mileage & time
commensurate with your driving habits &
atmospheric conditions & the
which you find the splines during the
servicing. Moisture condenses on the shaft &
with the in-out movement during
operation of the clutch & the wiping action of the
under torque, all conspire to move the grease out of the
splines. Late splines
hold up a better & longer, regarding
wear, if not lubricated, can lead to spline
failure, a $$$ situation.
I suggest a look-see & cleaning & lubrication of the transmission input splines at 15,000 miles since last cleaning & lubrication, & then adjust the mileage for the next following time, depending on condition.
End play on the input shaft can
cause a quite-grabby clutch
operation; that can happen cold and/or hot. More
often when hot. To fix THAT, one must remove &
open the transmission & work
shaft shimming. One can get an idea if that is a problem by
heating it to about the temperature of boiling water, &
measuring, with a
the input shaft end play. Anything over a few
thousandths of an inch is suspect.
This problem with transmissions causing
a grabby clutch is not overly common, but it
seemed to be
more so for the 1979
Grabby clutches can also come from a
somewhat rare problem, the
crankshaft has excessive end play.
HAS INFORMATION TO FIX THAT PROBLEM.
It is possible for a bad throwout bearing to cause a grabby clutch.
Recommended greases for the splines:
Because of my & others' testing of spline lubricants, over many years, & still going-on, I have removed all grease & greasing methods from this article you are reading, & placed them HERE: http://bmwmotorcycletech.info/chemicalsetc.htm
You will find ALL the information at item #6A in that article. Please read it carefully & fully...and, it is long.
EZ-Clutch (and variations): The pre-1981 clutches have a heavier pull at the handlebars, some dislike that, or cannot easily physically cope with it. There are several types of modifications to fix this, besides the HUGE expense of installing a 1981+ clutch with its necessary transmission work. Modifications involve a single pulley device or a lever arrangement. One that is available for purchase is from Craig Vechorik ('Vetch'), dba Bench Mark Works, (662) 465-6444; located in the USA. www.benchmarkworks.com/articles/howto/clutch.html. Bench Mark Works also has it available from their place in Canada. There is also a type you could build, that has some advantages over Craig's...as the original cable end can be used. Here is a website with photos to give you ideas: http://www.frankhams.freeserve.co.uk/temporary_uploads/ezclutch_page.htm
Do not install an EZ clutch pulley system until you are SURE the problem is NOT in the clutch lever, clutch cable, etc.
A factory or aftermarket tool may be used to centralize the friction disc when assembling the clutch. Centralizing is needed to enable the transmission input shaft splines to line-up with the clutch disc splines. However, your eyeball is good enough if careful. If you have a lathe and want to make this tool, it is, overall, is roughly 133 mm long; the length is NOT in the slightest critical. In fact, hardly anything is critical. I do suggest making the 20.7 mm diameter, as shown in the sketch, reasonably close to that. My measurements were from my factory tool: http://bmwmotorcycletech.info/CLUTCH TOOL.pdf
Here is a photo of all the factory-type tools for the clutch:
The threaded release tools are especially useful for the /5 clutch, but you do NOT NEED THE SPECIAL TOOLS. You can fashion something to hold any of the clutches from rotating while R/R bolts. You can use long cheap hardware store bolts & nuts to release the /5 clutch...etc....all as described earlier in this article.
Here is a hyperlink to my tools article: http://bmwmotorcycletech.info/tools.htm . In that article will be found information on clutch removal and assembly tools.
Here is a link to a site that has well-designed clutch tools (and, most every special tool you might want for your Airheads), highly recommended! Previously owned by Ed Korn! Many of the tools on this site are quite cleverly designed and the tools are well-built: http://www.cycleworks.net/index.php?main_page=index&cPath=29_33_52
If the full address does not work for you, then use http://www.cycleworks.net and click on the appropriate places for the tools for the clutch, or, whatever you are looking for. HIGHLY RECOMMENDED SOURCE!!
Here is a link to an aftermarket clutch disc centering tool:
Assembling the clutch:
1981 & later models have a lipped seal at the rear cover, not easily replaced....the
must come apart.
This lipped seal at the rear is for the clutch-operating pushrod. Install 1981 & later pushrods, oiled,
FROM THE REAR,
rotating it a bit, to avoid damaging
the seal (which you will, if you install
the front, like is done on earlier transmissions)
When you disassemble a clutch, for whatever reason, one of the things done is to check the friction disc for thickness. This means from one side to the other. I do it near the outer edge, and at about 3/4 of the way towards the center of the linings. Other checks are the spring (relaxed mode) height, & condition of the other parts in the clutch assembly. New friction discs are about 6 mm thickness with some variation, fractions of a mm, over the years. BMW says to replace the disc at 4.50 mm. On an Airhead, getting to the clutch is fairly easy, so whether or not to replace a disc at 5 mm or even a bit less, is a judgment call. You might consider letting it go, so long as the clutch is not slipping in top gear with heavy throttle & goodly rpm, all of which are worst case for slippage to occur.
One of the big decisions is what parts need replacing, if any, if the friction disc is going to be replaced. You may hear advice to replace all parts that push against the disc on both sides. But, how do you know? There are no specifications on the DISHING type of wear that IS one of the main reasons to replace those parts (& deep scoring, etc.). Some of us know what works, & what does not, & we might check 'dishing' with feeler gauges on a precision flat surface. Here comes your hint...
Measure the disc friction area near the outer edge, then in somewhat, & then near the inner edge. Do this with a micrometer, not the wide jaws of a vernier caliper. You may have to make up something to allow measurements near the hub. If the thickness is pretty good for all three checks, you are VERY LIKELY NOT going to need the other clutch parts. How much difference? Maybe 0.015" is about the maximum but have seen more that was OK. If less than that as a variable, you probably can just replace the friction disc. Some folks just replace the disc, & then soon have to do a clutch job all over again, due to not checking the wear on the other parts.
If the clutch parts are NOT "OK" flat, you can contact such as Southland Clutch to machine your plate & make you a thicker disc to compensate for that machining; or, purchase new parts. Southland Clutch; 101 E. 18th St., National City, CA, 91950, (619) 477-2105, can resurface all models of Airhead worn clutch parts & supply the thicker clutch disc that is needed after those operations. Dan Levine. Dan@southlandclutch.com
During your assembly (don't forget previous information on marking the parts & 120° assembly), I suggest you coat the edge of the diaphragm spring where it touches the flywheel & the fingertips areas too, all with thick moly grease/paste....AND not ver
Flywheels, clutches, and their bolts:
SOME 1980.... & all 1981 & later Airheads.... used Clutch Carriers, no longer are they called flywheels.
Did you have the flywheel off? Engine rotated some? Need to find out which
bolt holes & flywheel holes should be lined up? Five choices!.....
Here is an edited question & reply I did to the Airheads List:
" I removed the fly wheel at top dead center (OT mark) but when I installed the seal with the installation tool I ended up rotating the crank. How can I ensure that I am at top dead center so I can reinstall the fly wheel correctly?"
Since you have the flywheel off, I certainly hope you have a crankshaft stop of some sort at the alternator bolt. If you did not, you are in danger of doing major damage as you re-install the flywheel....so, do it...and hopefully the crank has not already moved forward. If you think it moved forward, see my article & the sketch from Tom Cutter....both are on my website. It is Article 60, sub-section 2. A direct link: http://bmwmotorcycletech.info/flywheelremovalwarning.htm
I am not in favor of removing that crank stop (so as to turn the engine with the rotor bolt), to find TDC, because if you should then allow the crankshaft to move forward, you could be in a world of trouble. The safest way for you to go would probably be the following procedure, which takes all factors into account, including rotor bolt threads direction for tightening/loosening. READ THIS ENTIRE SECTION BEFORE DOING THE PROCEDURE.
1. Remove the valve cover on the left cylinder & remove left & right cylinder spark plugs so the engine is easy to rotate. Remove the rubber plug that covers the timing window, located slightly rearward of the oil level dipstick
2. Place the flywheel into any bolt-hole positioning, lightly putting in a few bolts.
3. Rotate the flywheel slowly in the NORMAL direction, which is ANTI-CLOCKWISE as you face the flywheel from the rear. Watch as the left EXHAUST valve CLOSES. THEN, rotate more & watch the left INTAKE valve. After the INTAKE valve closes, continue to rotate... in small amounts.... shining a flashlight into the spark plug hole. You will see the piston come fully out, then reverse. The pushrods, piston at near or fully outwards, should be easy to rotate by your fingertips (assuming valves were set properly), & a double check is that both valves are fully closed.
You can skip removing the valve cover in step 1, & then skip step 3, if you feel OK about 'feeling' for the piston coming outwards. It does not matter which stroke you are on, just that the piston is close to being fully outwards. I often do it with the round-tipped tommy-bar in the standard tool kit, through the spark plug hole. Turn the engine (if you do it this way), VERY SLOWLY AND GENTLY so as to not let the tommy bar hang-up & bend the spark plug threaded-hole metal.
Early /5/6....to 1974
had five 10 mm flywheel bolts used on 93 tooth flywheels. There were
installed. I will NOT
reuse them. Torque them to book specifications,
The flywheel was 11-22-1-256-966.
/6 in 1975 and 1976 had five 11 mm flywheel bolts on a 93 tooth flywheel. The flywheel was 11-22-1-262-070. 11 mm bolts were used on all later models.
/7 for 1977 through early 1978, NON-emissions timing bikes had five 11 mm flywheel bolts on 111 tooth flywheels. The flywheel was 11-22-1-263-788.
1978-1980 WITH emissions timing bikes had five 11 mm flywheel bolts on 111 tooth flywheels. The flywheel was 11-22-1-336-380.
Flywheel mounting uses the mentioned larger 11 mm bolts on all models after the
10 mm bolts. Threads were ORIGINALLY to be clean & dry.
BMW Service Information bulletin (we call them SI's), November 1991, #11-049-91, sub number 2495, & this can also be seen on the 12/92 fiche on page 3, G23: Basically, it stated that while the flywheel bolts were previously at ~75 foot-pounds (100 Nm), they were now to be at 90 foot-pounds (125 Nm), this is with cleaned threads, BUT... the threads were to be OILED! BMW specifically said that the bolt limits would NOT reach their limit of elasticity at that torque, & could be REUSED! I will NOT tighten them that tight. Makes me very nervous! However, some do, and I have heard of no problems reported. It is YOUR CHOICE. NOTE also that this is in regards to the 11 mm bolts, & applies to 1981+ models....certainly not the smaller /5 10 mm bolts, nor the very early /6 10 mm bolts; which need replacement upon each use, which the 11 mm do not unless damaged. Those early 10 mm bolts on the /5 & early /6 are absolutely not to be torqued to such high values.
I use, clean & dry (or faintly oiled, by cleaning with kerosene with a BIT of oil in it), torques of 42-45 foot-pounds on the 1973 & earlier engines. For the 1974 I use 52-55 ftlbs. For 1975 & later up to the 1981 models, I use about 75 to 80 ftlbs. I use about 80 ftlbs, clean & dry threads, on 1981+, but am OK with slightly oily, if you wish. You could certain just use 50 ftlbs on the early engines, and 80, oiled, on the 11 mm bolts, but be cautious.
Clutch Adjustment& Clutch Cable Problems:
32-73-2-324-956 cable is 1460 mm or 1495 mm long; the sheath is 1285 mm long. This cable may have been 32-72-1-235-744?
32-73-2-324-958 cable is 1385 mm long; the sheath portion is 1155 mm long
32-73-2-324-959 cable was used on R65 Euro, 86+RS. 1386 mm long
32-73-1-230-041 cable is 1320 mm long; the sheath portion is 1085 mm long
32-73-1-230-042 cable is 1460 mm long; the sheath portion is 1225 mm long
3273959 is 1361 mm long, sheath is 1130 mm. Needs confirmation. Believe was on R45/R65
3273694 is 1469 mm long with 1242 mm sheath, needs confirmation, believe was used on R45/R65 with high bars.
32-73-2-324-956 cable is 1520 mm long, the sheath is 1285, used on GSPD, some others.
32-73-2-324-960 is 1625 mm and is on K1100LT
3273957 is 1410 long, sheath 1180, used on R80, R100, Mystic
The above information could have errors.
I have a LOT MORE information on various clutch cables, used with various bars, etc.
See www.siebenrock.com for more control cable information
Below is a snippet copy from my control cables article covering WHY cable problems arise. Below this box are more details.
|1. Throttle cables on the Airheads: LEFT cable fails at the carburetor
due to the throttle cable being bent during accessing the oil dipstick.
2. The bushing at the clutch lever casting assembly at the handlebars that the clutch lever rides on wears (on BMW's it is a Nylon-like material). The result is the lever being able to move up and down, allowing angular motion. If loose enough, the stranded core of the cable would start rubbing on the sharp-edged guiding slot in the lever. Eventually a strand would break, failure came soon as more strands broke. The bushings are easy to replace and not expensive. They may require slight reaming to fit. The sharp-edged slot can be filed smooth.
3. Poorly made cables, & NOT ALWAYS AFTERMARKET ones. The areas of poor cable manufacture are generally at the barrel tip area; some hand work will fix it. Be sure the cable end barrel's can rotate smoothly & hand file the barrel, sometimes the crimped part at the end needs attention too, depending on maker.
4. BMW cables are plastic-LINED & last a long time, & SHOULD BE SMOOTH with little friction. Lubricate barrels with moly grease or moly-oil during assembly. This also applies after gunk/wash jobs: re-lube those barrels! In some instances the rounded area of the fork in the clutch lever at the transmission (where the BARREL FITS), fits too tightly.
5. Failure to route the cable properly...typically resulting in too-tight bends or insufficient flexibility, due to using too many cable ties to the frame (only ONE for clutch cable), etc....so the cable was too rigidly mounted.
6. Lubricating BMW cables innards....lubrication attracts abrasive dirt and may (?) swell the liner (a Nylon-like material). DO NOT LUBRICATE CABLE INNARDS.
***Breaking Clutch cables often?....see above red box area...and below:
BMW clutch cables are lined with a plastic material. DO NOT OIL THE INNARDS. The ONE exception was the earliest /5 bikes, which came from the factory withOUT the nylon-like internal lining. I suspect only a few low mileage /5 bikes are around these days with those earliest cables. Aftermarket cables generally do NOT hold up, and do NOT operate as smoothly, as they do not have such linings.
BMW's cable suppliers have sometimes done a lousy job. Some BMW replacement cable barrels do not rotate smoothly; you should file them so they do. A nastier problem is the top (at bars) crimped portion that do not fit the lever slot properly; there can be interference; the cable will foul on the lever. BE SURE TO FIX THAT; use a fine not coarse file. Another problem (reported to me) has been MISMARKED CABLES....wrong lengths.
Be sure the clutch cable is routed properly, & tied down only once at the frame. That tie, which must be only barely moderately tight, should be located roughly midway down the right side frame down-tube.
There must be NO broken cable strands.
The clutch lever at the bars should not have excessive angular UP & DOWN play; if it does, the nylon bushing IN THE BARS LEVER AREA needs replacing; make sure the waverly washer IS in the lever depression area for it. BE SURE that with lever movement in any direction (in-out, up-down) the inner cable strands are NOT being rubbed against by the clutch lever slot. Be SURE the barrel rotates easily... lubricate the barrel and the transmission ends with moly grease. If the barrels do not rotate smoothly without lubrication, fix the barrels or the transmission lever curved area (many are slightly too small in curved area size).
The adjustment is not supposed to be exactly the same on all models. In practice, while the "new method" will work OK for all Airhead Clutches, I prefer to use the old adjustment method for the early clutches. The 1981+ clutch adjustment MUST be made with the new method. My recommendations are below:
1. For pre-1981 clutches (some few 1980 had the later clutch with carrier):
The adjustment at the lever at the back of the transmission sets the free-play clearance at the BARS lever; the adjustment of the outer cable sheath at the BARS lever sets the angle/distance of the lever at the back of the transmission. You want to end up with about 3 mm free play at the bars lever JUNCTION, that is, the outer angle of the lever to casting assembly. When the bars lever is ~ half-way through its actual pressure range, the clutch lever at the rear of the transmission should be approximately PARALLEL with the transmission rear case. When you are done you should ALSO have APPROXIMATELY 2 mm of free play at the lever at the transmission rear cover.
2. For 1981+ clutches the adjustments are done a bit differently:
The difference is that the distance measured from the forward surface end of the barrel in the fork of the transmission-located lever, to transmission case where the cable comes rearward-through, should be 201 mm. There are also factory books that say 201 to 203 mm. BMW was never really clear on what part of that barrel the measurement was to be from...rear edge? middle? forward edge? As I noted, use the forward part of the barrel. The TOP cable adjustment...yes, at the BARS, sets that 201 mm distance.
The next adjustment is the bolt & its locking nut in the lever at the transmission. Adjust for 3 mm of free play at the bars lever. If you do not know how to do this, loosen the adjustment at the transmission lever a fair amount. You can now move the handlebars lever easily, & if moved far enough, you meet goodly resistance from the clutch. The amount of 'easy' movement, with NO clutch action, is to be such that the lever opening is 3 mm.
When the bars lever is not being touched, the transmission lever will be ~4° leaning AFT of the transmission rear cover. There is NO NEED to try to measure that angle, just know that with #1 eyeball on the transmission lever, it IS to be slightly angularly rear leaning. Make a simple tool from a piece of coat-hanger or whatever, marked for 201 mm, to check the 201 mm as noted in 2. first paragraph, above. Do these checks and adjustments with the engine COOL.
The reason the clutch levers are set this way is to ensure that the transmission lever
in the most efficient leverage position.
If you do NOT adjust it this way, & have the lever too rearward on the 1981+ transmissions, the rubber boot at the transmission clutch rod area will, or can, LEAK OIL.
Be sure that you set the 201 mm distance and the bars lever distance correctly!
Now & then someone will complain that their bike, after sitting for some time, more often in
areas, has a clutch that has "failed or is stuck". You can pull the
lever back, perhaps it even feels normal, but
the clutch will not release & if you put the transmission crashingly into gear, the engine stalls.
The problem is that the clutch disc has frozen to the adjacent parts. You can fix it by replacing all the clutch parts with the latest items, which are not cheap...OR, you can try to force the clutch to disengage. There are several methods, including pushing the bike & shifting into second gear....etc. I suggest you don't pry at the clutch through the ignition timing hole.
I prefer to try the following things in order shown; it can take two or three tries!:
(1) Put the bike on the center-stand; SECURELY jack the bike at the rear frame crossover (swing arm area?), ....just have the rear wheel a bit off the surface. HOLD the front brake! Start the engine in first gear. Do not touch the clutch lever. At some moderate rpm, suddenly snap the throttle off (keep that front brake ON!) AND give very hard pressure with your right foot on the rear brake. That may force the clutch to release. Try twice. If no help, go to step (2).
(2) Warm up the engine, so it starts easily. Push the bike to the street. Start the bike in FIRST GEAR (depending on model, you may have to pull in the clutch lever at the bars to allow the starter motor to crank the engine to restart the bike). Ride the bike down the street at 5000 or more rpm in first gear. At a convenient & safe time, suddenly pull in the clutch lever at the bars & hit the front and rear brakes VERY HARD. Try this up to three times. If no luck at all, you will have to remove the transmission, & work on the clutch...or, try prying at the clutch through the timing hole...which I have suggested you do not, but if carefully done MIGHT work..
01/26/2008: all prior revisions incorporated, and much added from old obsolete engineinternals.htm
05/04/2008: Edit section on the plastic throwout bearing piston problems.
04/16/2009: Clarify a few details. Re-arrange order of presentation of items.
10/27/2009: Clarify a few things, fix and add hyperlinks.
11/04/2009: A few additional clarifications on R65/R45 clutch bolts; and re-arrange article somewhat, it was excessively gaudy.
06/24/2010: Clean up article some
04/29/2011: More information, such as a link to factory clutch tools picture on this site, etc. NO errors found. Strictly a clarifications.
06/16/2011: Add Stuck Clutch section, minor other clarifications, quite minor
09/08/2011: Fix typo in part number for the early eighties heavy-duty diaphragm spring; was 2121338508, should be 21211338508.
10/02/2011: minor clarifications (which I forgot to upload for months)
03/28/2012: add note and hyperlink to my tools article.
04/08/2012: Very minor clarifications on throw-out bearings.
06/08/2012: Completely re-do the clutch levers adjustment area for clarity; clean up excessive use of fonts, colors, emphasis.
06/25/2012: Expand upon stuck clutch information
06/28/2012: Clarify cable problems and clutch adjustment.
09/04/2012: Add section on setting flywheel & crankshaft alignment. Add QR code; change Google ads arrangement; add language button.
12/12/2012: Remove end play adjustment details, as is now in the flywheel removal article, 60-2
12/24/2012: Add paragraph on clutch wear dimensions.
04/28/2013: Clarify a few details, remove some redundancies, clean up article, add hyperlink to the disc alignment tool pdf.
05/16/2013: Expand section on throwout bearing parts, add emphasis and update due to a bad late style in a R100R that was reported.
08/15/2014: Correct item 3 from CW to CCW; correct flywheel number from -906 to -966
03/17/2015: Make sure hyperlinks work properly
07/22/2015: More information re: lwr end of clutch cable barrel & the arm & add section on greasing splines, removing prior information.
12/09/2015: Go through entire article. Increase font size, change separation lines, fix meta codes, duplications, etc.
02/04/2016: Begin minor updating, and completion of 12/09/2015 items not then fully finished.
05/24/2016: Font reductions; eliminate many b-grd font color changes, update metacodes, scripts, & layout, revisions 4 clarity, eliminate redundancies, etc.
Return to Technical Articles LIST Page
Return to HomePage
Last check/edit: Saturday, August 20, 2016