I recommend you read the clutch article: http://bmwmotorcycletech.info/clutch.htm
I thought about combining these articles, but the result would be too long.
Applicability: All BMW Airhead motorcycles, /5 and later.
Some applicability to Classic K-bikes & other BMW motorcycles with transmission input splines that work with a dry clutch. The K75 and early K100 K bikes not only have splines at the input of the transmission, but have splines at the driveshaft output area...that is, the rear drive input. ALL MUST be kept lubricated.
Skill level: For input splines on Airheads...lower intermediate or better; for Classic K-bikes for rear drive/rear of driveshaft splines, skill level is same. For K-bikes input splines, skill level: solid intermediate or advanced. For the throwout bearings & clutch arm servicing of all these bikes, moderate skills needed.
Dozens of greases for the transmission input spline have been tested. Instead of repeating information and trying to keep the article updated here, see for recommendations: http://bmwmotorcycletech.info/chemicalsetc.htm
NOTE: The Airhead swing arm bearings are the common number 30203A, although 30203 can be used. One is sealed, one not, I prefer the UNsealed ones. The pre-1985 wheel bearing number (all but certain R65 models) is also the 30203 series. Early models call out use of a gasket ring, 31-41-1-233-252 or 31-41-2-000-331. These are 22 x 40 x 10 mm. I do not use them. The reason is that they do not stay seated when grease is pumped-in.
Besides avoiding SPLINE WEAR from rusting & helping with such as fretting corrosion; cleaning & re-lubrication of the transmission input shaft splines will make operation of the clutch smoother, & shifting smoother/easier. If the splines dry out or begin to rust, shifting will get progressively worse, particularly downshifting. If kept properly lubricated, the splines may last almost forever, which is good because replacing an input shaft is expensive because of parts cost AND the entire transmission must be overhauled & re-shimmed. The clutch splines (this means the transmission input shaft splines as you should probably not grease the clutch disc splines themselves), are fine toothed; the teeth not deep, & dryness & rusting (or what appears to be rusting) causes $$$ problems. It is likely that condensation of moisture on the splines as the engine cools off....much worse in high humidity areas.....causes accelerated loss of lubrication. The normal use of the clutch causes the clutch disc splines to slide back & forth along the transmission input shaft splines, wiping away the grease. The grease will tend to disappear after some mileage; & rusting & other serious wear then begins. You do NOT want that to happen. MANY different greases have been tried, including some with very sticky, gummy or even taffy-like qualities (with & without molybdenum disulfide, which is usually just called MOLY). If the clutch splines wear enough, you will hear a very uncomfortable noise, & then you are not going anyplace, as you just ripped off all the splines. Long before this, with dry splines, it is likely that your downshifting will be poor.
WHY did BMW use MANY small and not overly deep splines at the transmission input shaft?
...what about the rear wheel splines (twin shock models):
For a given diameter, the use of smaller splines...since you have many more of them... are stronger due to the driving/driven edge contact total area being larger....and the stresses are spread out more. As the DEPTH of the splines increases, you have another factor involved. Small & numerous but not too deep fine splines are the best. Proportionately, the larger deeper type of splines will have more friction...not a good thing for a clutch disc & not for the rear drive either, for friction/heat/wear. All this can be proven mathematically, but it is a bit complex. There are numerous form-factors for splines; the ones that have tapered sides are the harder to analyze...and would require a very large expanded sketch.
Think about it this way: Let us suppose you could make the splines fit nearly perfectly at all contact areas & tightly in all directions, yet they slide fairly easily. Then you started making the fit have more clearance, more slop. As the clearance between the male & female teeth is increased from the rather tight barely-able-to-be-assembled-with-oil point, to a nice smooth fit;....& then further to where noticeable backlash (even a few thousandths of an inch) is possible....the teeth will no longer contact so much along their full side surfaces as pressure is applied. The teeth now begin to contact at the more outer areas, primarily on ONE SIDE when under power, & the other side when the throttle is shut off, all due to the shaft being circular and contact now becoming more angular. You have not only sliding surfaces trying to wipe off grease, but IMPACT pressures as power is on & off, & some other terms can apply besides impact.
To further visualize this, think about the teeth being on a circle, sticking up from that circle at 90° from the surface. TWO things you should notice: First, that if you expanded the diameter greatly, you could see with your eyeball that the teeth are not at EXACTLY 90°, due to being on a circle. Secondly, as the parts turn, any free play from a tooth not being dead-solid to the engagement tooth, cannot contact fully over the side surfaces, but are actually WIPING as they move with respect to each other AND that wiping is such that only the more and more outer part of the sides of the teeth is in contact, and that becomes more and more so as the clearance between the teeth increases.
This is, in a way, how straight-cut gears engage each other! Think about that wiping motion! Not only is the force now being concentrated more and more at the outer part of the teeth, but the lubricant is being wiped away....and the teeth are also sliding in and out with respect to each other, every time you use the clutch. Even when NOT using the clutch, the teeth are wiping back and forth as the throttle is on and off. The purpose of the lubricant is to enable the best sliding AND protection from being wiped away from heat & cold changes, & some quite (one hopes!) goodly protection against effects of humidity & dew condensation, etc.
For the nerdy, there are all sorts of official names that go with 'wear' on various metal parts that contact each other. Fretting, brinnelling, impact corrosion, rusting;....and more. Some are seen at the transmission input shaft...and some are seen at the output drive splines (twin shock airheads). Some are seen on early Classic K bikes at the input of the rear drive.
For the Airhead rear wheel splines, what I will call impact corrosion is a problem. When you shift up or down abruptly, and use abrupt throttle movements, the suddenly large forces try to spit out the grease from the wheel cup splines. Since the torque can be huge here due to gear ratios, ETC.... & in-out sliding is almost non-existent... and, we hope, rotational slop is low, impact forces are the primary concern. If you make the fit too tight, you cannot put the wheel onto the rear drive. If too loose (or worn), the forces wear the metal, one way or the other. The sloppier the fit, the faster the wear.
A more or less ideal lubricant for the rear wheel cup splines would probably be a very nastily thick TAR, but that would keep you from being able to remove the wheel for tire service!
After the mid-1980's (starting, supposedly, with the Monolever bikes of 1985) BMW was said to nickel-plate
the transmission input shaft splines & re-greasing can supposedly go to 30K miles. I AM NOT CONVINCED. Sometimes yes, sometimes NO.
MY suggestion: No matter what type of weather you live/ride in (even wet or humid areas where re-greasing is going to likely be needed sooner)....>>for your first check on the input splines, I suggest you check the splines at 10,000 miles since the last lubrication (& if unknown, do it NOW!). If OK, go to 15,000. Extend 3,000 for each following, then back off when you see ANY rusting-look, etc. I doubt you will be able to go much over 24,000 miles, no matter the type of shaft, plated or not, on AIRHEADS. I have almost never seen any un-plated ones go much over 18K. FEW of the plated ones go over 35,000 miles. For those that have combinations of these things: short rides, shifting a lot, high humidity climates... ESPECIALLY if engine cool-down is in a high humidity area..........YOU WILL need re-greasing more often than those in dry desert climates, or those who do mostly long rides. Every time you shut the engine off after a ride, the engine cools, the internal parts, including the clutch parts, condense some moisture on them, particularly in high humidity areas. That can promote 'washing out' the grease, rusting at the shaft.... unless the grease is still intact. For smooth operation I prefer quite a bit of moly in the grease (~30% does seems adequate however) as moly tends to protect the metal from some forms of wear, and tends to remain slippery, and even works itself into the metal somewhat.
I have removed the discussion of various greases from this article. For an in-depth discussion, see article #73.
That is: http://bmwmotorcycletech.info/chemicalsetc.htm
Step by step HOW-TO: inspection, cleaning and lubricating the input splines:
While the procedure was developed from both a 1983 and 1984 R100RT, because they happened to be at my shop being so-serviced at the time, some generic information is included, & this procedure should be easily adaptable for YOUR bike. There are specific reasons I did certain of the steps in the order shown.
This procedure does not require many special tools. Tools from your on-bike BMW tool kit are needed. See item #11 below for a few things you will need. Also needed are the proper grease for the splines; a grease gun with a rubber tip that can contain almost any type of chassis grease (for the swing arm greasing); a modified 27 mm
or modified 1-1/16th inch socket; a torque wrench; 13 mm socket; 3/8 or 1/2 inch drive wrench, probably with a 4 or 6 inch extension; 6 mm allen wrench square drive; 6 mm standard BMW tool kit Allen wrench, with the short side shortened...this is for the lower left transmission bolt; anti-seize compound, rags, cleaners; two acid brushes (modified); and two pieces of almost any small rod (wood dowel is OK) and a few minor items you
are very likely to have. It is handy to have a MODIFIED jack: http://bmwmotorcycletech.info/hydraulicjack.htm.
These tools are not to be construed as an exact list of items you will need. You may improvise for YOUR bike as needed. Some folks with smog parts may need a 15/16" flare nut wrench or substitute.
NOTE: You can elect to totally remove the transmission. If so, you may have to remove the driveshaft housing, shock absorbers, battery tray, etc. There is no question that a total removal allows a better over-all job and allows a nice inspection. You gain access to do a very thorough cleaning & re-lubing, checking condition, etc., of the swing arm bearings, & you can more easily get into other areas...including the pesky hard-to-get-to rear brake switch and linkage... for inspection. A total removal of the transmission is not difficult....but does take more time. I do recommend a full removal at least every 40,000 miles or 6 years, whichever comes first.
REFERENCE: 07-11-9-918-655 50 mm Allen head bolt with captive washer; 07-11-9-901-033 45 mm bolt or 07-11-9-901-161 40 mm bolt. In case you decide to replace the upper right stud. See text, in item 6.
Regarding the modified 27 mm or 1-1/16" socket:
Obtain a standard 12 point socket, NOT a 6 point. 3/8" or 1/2" drive, to match your existing torque wrench (or, get an adapter between 3/8 and 1/2). Square off the large working END of the socket until all of the small amount of INside taper is gone. You can do this BEST by chucking the socket in a lathe; but can be done if VERY careful about flatness AND squareness, using a grinding wheel or flat sander. The lathe does the very best job, and it REALLY is worth having this done properly if you do not have a lathe. This first modification of the socket is just to eliminate the taper in the working INSIDE END of the socket. The socket needs one more modification. Remove one of the plastic caps over any one swing arm adjustment area. Take a careful look at the inside diameter(s) of the swing arm nut/adjuster cavity. You will probably see TWO diameters. These VARY with how the factory assembled your frame. Turn the outside of the socket on a lathe, or by hand on a grinder (crudeness is OK for this), so that the socket will fit very easily through both diameters in the swing arm cavity and the newly 'made square' end of the socket fits FULLY over the thin 27 mm nut. Do not turn/grind the socket too much, nor too little. Too much and the socket is weakened (another reason for a 12 point, not 6 point), too little and the socket will not pass easily by BOTH of the internal swing arm cavity diameters, particularly on some bikes. SOMEtimes BMW did machine those two diameters concentric and very nearly the same size. It is very important that the socket fit squarely and solidly on the thin 27 mm locking nut. See near end of this article on how to adjust the swing arm if you want to skip to there, now.
1. There are two articles, besides my http://bmwmotorcycletech.info/clutch.htm article on this website, that you might want to read, and use the information in those articles as an adjunct to THIS article. Those articles are located at:
http://www.airheads.org. Read the articles on the throwout bearing by Matt Parkhouse, and mine, on Lubing the Transmission/Clutch Splines. Those articles may prove useful to you. Reading those two articles may give you somewhat different perspective on the article you are presently reading.
2. Remove the gas tank. Engage 5th gear on the transmission (4th on /5) and leave it engaged.
3. Remove the clutch actuating arm at the rear of the transmission. There were several styles of these arms. If you have a /5, you have a cotter pin to the boss; no problems with them. A bit later came a type used for some years: This type uses a steel pin that has a circular groove, with a C-clip, and the clip is located at the LOWER area of the INSIDE between the transmission ears. If you have the C-clip type I HIGHLY RECOMMEND you do a modification, a very simple job. See my http://bmwmotorcycletech.info/clutch.htm article. If you fail to do this modification, and the clip falls out and the pin comes partially out (it may disappear too)...then the very next actuation of the bars lever will BREAK OFF a transmission ear, stranding you. The early style arm also has a grease fitting, and the throwout parts are different. The much later style arm uses a 10 mm bolt with waverly locking washers, and NO C-clip. ((Insert the bolt so its nut is at the LOWER area. Yes, that is a bit of extra insurance)). I prefer a Nyloc type of nut. The later arm has no grease fitting, last version had needle bearings. Some have modified the Airhead arms...& the K-bike arms... for grease passageways and a zerk. I consider this to be of much more value for the K bike.
4. If the arm is of a late style, push through the steel sleeve (if you can easily) and in any event do clean the arm bearing and lubricate it with OIL. I coat the outer faces (where the arm rubs the transmission ears) lightly with moly grease. It is QUITE common to see
arm needle bearings as having NEVER been cleaned and oiled since new. I usually use a bit of heat on the arm and then soak the warmed arm needle bearing area in a mixture of a light solvent and thin oil, and try to get the needles to be movable. DO NOT use a moly grease.
Remove the throw-out bearing. Do not try to remove the inner central rod that is forward of the throwout bearing. The earliest style throwout bearing had BALL bearings. A later not-as-good style had a flat radial needle/roller bearing, and after 9/80 it is a ball bearing again (maybe). Don't bother trying to convert to another style. There are some variances in the outer spring, black rubber cup, and the single or two part piston, ETC. Ball bearing types have been seen on years they were not supposedly on. There can be problems with the throwout bearing ... the clutch article goes into it in detail, particularly about a tolerance problem with the later ones. DO READ IT: http://bmwmotorcycletech.info/clutch.htm. IF you have cleaned the throwout bearing it is a VERY good idea to lubricate it with a very light non-moly grease before reinstalling it, as the throwout bearing does not get gearbox oil lubrication for some time after you reinstall it, from gearbox oil movement.
Set aside the now cleaned and lubricated arm and throwout associated parts. It is MUCH easier to move the transmission far enough to the rear for input splines greasing, with the clutch lever removed. In fact, without the lever removed, you probably can not gain proper access. DO NOT injure the transmission ears in any of your work!! KEEP FILTH AWAY FROM THE PARTS YOU JUST CLEANED AND LUBRICATED.
5. Remove the air filter and all of the airbox. If you have the older clamshell type housing you will have to push the breather hose out of the half. If you have the later rectangular housing, and depending on what is in the area (pulse air parts, breather hose setup, vacuum line setup, etc.), you may have to move the breather hose forward. Replacing it can be a bit of fun, and it is easier at that time, to simply remove the starter motor cover (I recommend disconnecting the battery, probably remove it now... BEFORE removing the starter cover to avoid sparks)...and you CAN do that now. With the starter cover off, it is a good time to check the nuts on the electrical posts of the starter and solenoid switch. If you've have had oil breather problems, now is a great time to fix whatever is wrong. On late model Airheads, you can inspect the solenoid valves and vent into the crankcase, and decide whether or not to modify them. You may want to change an early model disc breather to the later reed type & clear the bottom of the cavity small drain hole in the breather area (no drain hole on models prior to ~1978). There is nothing wrong with using the original early disc-type breather if in good condition; you could even make a replacement for the disc if poor...and a few folks are making them for sale (see my references article, http://bmwmotorcycletech.info/references.htm
http://bmwmotorcycletech.info/oilsketch.htm has all the breather information, well down that page.
6. Remove what vacuum, fuel solenoid and vent solenoid & smog parts, if any, that you have & need to or want to, on your particular bike (you may want to modify at this time or before re-assembly). You may want to read this article: http://bmwmotorcycletech.info/pulseair.htm
Remove the left lower bolt on the transmission & the right lower bolt. NOTE the brown grounding wire at the left lower bolt if you have that. Pay attention to washers. Remove the upper bolts.
HINT: consider the right upper bolt or stud, depending on what you find. Think about how much easier it might be in removing the transmission, if it was a bolt, and not a stud. It is easy to change!
If you decide to remove the transmission:
Unfasten the driveshaft U-joint from the transmission, remove the swing arm adjusters. This is where you use that modified 27 mm or modified 1-1/16" socket. This is a good time to inspect the 4 special bolts that hold the U-joint...they must be the correct later shorter length NO lockwashers! Loctite blue may have been used on the threads.
If you have the rectangular airbox, remove the 13 mm hex headed bolt that goes straight down through the top middle of the airbox into the transmission. Removing that 13 mm headed bolt is NOT needed on the clamshell airboxes. IF you removed the bolt, then when you REinstall that bolt later, coat the first few threads AND THE WASHER with a non-hardening thread sealant, such as Permatex Form-A-Gasket #2. DO NOT USE the hardening version. If that bolt is loose, or leaks, oil will be sucked out of the transmission. If you have the rectangular airbox, you should now be able to remove the base box.
NOTE: BMW uses metric size vacuum and fuel crossover hoses. Use of SAE (American, inch size) hose will make for more difficult fitment. I recommend the new type NON-fabric-covered BMW black hose. If you have a classic bike & want to keep it original-looking, you can get silver-cloth braded fuel hose from Bing Agency or VW dealerships, or some Independent BMW repair shops. I don't think it lasts as long as the later black BMW metric fuel hose. The longest lasting and the very best hose is a special clear or faintly greenish plastic type, see my other articles.
7. HINTS! Some folks have a hard time removing and replacing the plastic input tubes to the carburetors. On some few models, these tubes are not the same, left to right, and may not be the same end for end, and only one fits the proper left or right side, and only one end of THAT fits the airbox and carburetor. MARK yours and their ends before removing! (such as: "left, to carb"; or, "right, to carb"). For the rectangular airboxes, and to some minor extent the clamshell type, FOR THE PURPOSES OF THIS ARTICLE WHERE YOU ARE REMOVING THE AIRBOX, it is easiest to leave these plastic tubes attached to the airbox half or base, and to loosen the clamp(s) at the carburetor end of them and when the the airbox is removed (especially, the rectangular box), the whole assembly lifts off easily, and replaces easier. If those plastic tubes are off and the rectangular box is already installed...,try re-fitting the carbs and intake hoses and plastic tubes all as one assembly at one time as you re-assemble the bike. If the airbox is in-place, and you are just R/R the carburetor, loosen the band clamps on the head side of the carburetor, and the ones on the input side of the carburetor, and then angle-out the carburetor and air tubes. Same, in reverse, for reinstalling.
8. Using the Chinese jack from my article as modified, http://bmwmotorcycletech.info/hydraulicjack.htm,
or some other means, typically at the rear lower frame crossover tube (not as easy for a model with the pre-muffler under the transmission area); jack the rear tire barely off the ground. If you have a ride-off stand you may want to find a way to put a 3/4 inch or so piece of plywood under the ride-off stand by rocking the stand left/right, as you install a board. Bikes vary, play with yours until you find out what is needed. Remove the plastic covers over the swing arm adjusters, and loosen the two 27 mm nuts with the socket you modified, maybe only 1/4-1/2 turn loosening is needed, and then UNscrew the allen-center adjuster on each side, and REMOVE the adjuster-pin with the nut still attached.
You have to wiggle the tire/swing arm a bit to allow the adjusters to be removed, & that helps avoid damaging the adjustor-pin threads. I have seen bearings not lubricated properly & badly rusted, & cracked! If yours are bad, or really need a full clean & lube, then I recommend you remove the entire rear end of the bike & service the swing arm bearing area. Various pullers are available to remove the outer bearing race. Ed Korn (see http://bmwmotorcycletech.info/tools.htm article) made a cute one in a kit to also install the new one. It is a simple job. The swing arm bearing is basically the same as the pre-1985 wheel bearing, a common type from any bearing supply company. I prefer to NOT use sealed versions of those bearings (or, I remove the seal), allowing me to better grease from the outside, after the bike is reassembled, via the center Allen wrench hole in the threaded pin adjustor, using my greasing tool with the rubber tip.
9. There is sometimes no need to undo any shift linkage for just a BASIC spline re-lubrication. You DO have to undo the wing-nut on the rear brake rod, if you have a rear drum brake.10. Pull rearward on the transmission. It will likely come backwards a bit. The limit for the rear movement is typically not the clutch ears but the driveshaft housing interfering with the frame cross tube. You will probably find you need to HOLD the transmission backwards. While you can use some pieces of WOOD (NOT METAL!!) to wedge into the transmission-engine opening (and may end up doing that anyway), you MAY want to fashion some means to KEEP the suspension/etc moved to the rear. I do this by hooking a STRONG bungee from a lower spring/shock unit, back to the turn signal tube or rear rack, VERY tightly (on both sides if a twin shock model). If you play with the transmission and rear end movement a bit, you will find that you can separate the transmission from the engine JUST enough so that the input shaft forward end is visible. You can also use the method in the next paragraph:
NOTE! If you see an OILY spline at the transmission & see oil coming from the input end of the transmission, you MUST undo the universal joint, remove the transmission entirely, & replace the transmission input seal. Failure to do so will result in eventually oiling the clutch. This is an easy job if the transmission is out, you do NOT have to take the transmission apart.
Ideally, the transmission, when in the bike, is now back far enough to see the end of the input shaft I have mentioned. It is nice to be able to then move the center rod to the rear just enough to get to the rod tip with one droplet of lube, later.
11. Blow out any dust and dirt from the area. Do that now, rather than later. DO NOT breathe-in that dust. Under NO circumstances do any prying with metal tools that will nick the transmission-engine mating surfaces, thereby causing the transmission not to re-assemble dead squarely to the engine. CLEAN the splines of the INPUT shaft (NOT clutch disc!)....but...if the splined center of the clutch disc is very greasy, clean with a rag the OD and ID. DO NOT SPRAY SOLVENT ON THE DISC SPLINES.
To both clean and grease the transmission shaft input splines when the transmission is still in the motorcycle, I made up TWO simple tools:
Use two common "acid brushes". This is a small brush built into the end of a tubular piece of thin sheet metal. You can get them at most hardware stores, or Harbor Freight has quantities, cheap. Cut the bristles down in length, by maybe nearly 1/2, so they are stiffer. Tape or otherwise securely tie each brush to some sort of thin rod or any similar items, such that the brush handle length is extended. ONE brush tool is your permanent tool for cleaning the input splines, the other is for your permanent tool for greasing those splines. You only need make these two tools once, so after you are done with them, clean them and put them on your shelf of BMW tools. I use wood dowels from the hardware store to which I attach the brushes with tape. I am guessing my dowels are maybe 3/8" in diameter.
To clean the transmission input splines, use some sort of strong petroleum-based solvent on one of the brushes; move the brush back & forth the TRANSMISSION INPUT spline. I brush FROM the transmission TO the end of the spline. Rotate the spline as need be, by rotating the rear wheel, which is off the ground & the transmission is still in top gear. I like to finish this spline by spraying a good cleaner on it, but remember, do NOT spray clean the spline of the disc!...except you can poke & wipe with tiny rag pieces if need be (You CAN use a SMALL AMOUNT of solvent on those tiny rags). If you spray solvent into the clutch disc splines, that can put grease/oil/grunge, into the friction disc....so do NOT do that. Common BRAKE CLEANER does NOT do a good job for cleaning; in fact it is LOUSY. I use acetone, MEK, or similar strong and fast evaporating solvents. I also have used Berryman B12 Carburetor and Choke Cleaner in its spray can, with its spray wand, ON TRANSMISSION SPLINES.....avoiding the seal.
IF that area shows OIL leakage from the transmission, remove the transmission and replace that seal...and ask on the Airheads LIST or check my http://bmwmotorcycletech.info/transmission.htm article on how to do that! It is not difficult & you do not need to disassemble the transmission. Failure to replace a leaky seal will ruin your clutch eventually. There are TWO ways transmission oil can get into your clutch. ONE is via a bad transmission input shaft seal. The other way is a missing round tubular FELT, that can be somewhat of a devil to install, located, hidden, around the rod that passes from the rear throwout bearing area to the tip of the input shaft, on all early models. It is easier to install the felt from the forward nose (input shaft spline end). If you have NOT removed the transmission, you have likely not been able to remove that rod accidentally, so, you should have no problem with that felt at this point, as the felts last darn near forever. Later models do not have a felt, but a seal, located inside the rear of the transmission, and that is NOT simple to replace, and the rod is differently installed.
Grease the INPUT SHAFT splines once the solvent is totally evaporated. Work the grease into the splines, bit by bit, all around, using your greasing brush tool. It is not needed, nor desirable, for too much grease. Moly greases work best, see my article on chemicals, etc., here: http://bmwmotorcycletech.info/chemicalsetc.htm
If the rod END that is in the center of the input shaft is not visible, make it just visible. This is usually easy with the clutch lever having been removed at the rear, just a slight push on the rod. Put ONE SMALL drop of the moly grease on the tip & putting a drop at the rear where the clutch lever operates is a good idea too.
Clean the surfaces of the transmission case shell that will contact the engine surfaces. Take your time to do this properly. Under NO circumstances are any nicks, nor filth allowable, that would keep the transmission from SQUARELY & FULLY mating to the engine surface. Clean the engine mounting surface too. Keep in mind that a prior owner or workman could have left nicks which could keep the surfaces from mating 100.000%. Fix any such things. Since YOU did not use metal tools in prying the transmission-engine apart, YOU did not leave nicks. RIIIIGHT?
12A. Reassemble everything, bit by bit, slowly, and carefully. This is the last moment you have to install a change at the upper left engine case fitting, so decide if stud or if bolt.
INSTALL THE TRANSMISSION. Do NOT allow foreign matter to interfere with the transmission coming up to the engine cleanly, squarely, fully. Be sure the transmission is fitting squarely. If the transmission input spline will not engage the clutch disc, rotate the transmission output flange slightly (or rear wheel slightly if transmission flange is still bolted-up). Cinch up the bolts, evenly, in a cross pattern.
Do not forget the vertical 13 mm bolt (you HAVE used a soft non-hardening sealant on the bolt threads, under the bolt head and both sides of the washer?). The clam shell model requires the right-side clam shell to be in place for this. Do NOT forget the grounding wire at the left lower bolt. You can now reinstall the throwout parts & the clutch lever at the rear. Do any cleaning and lubrication there that you did not do previously.
12B. Centralizing & adjusting the rear swing arm:
After the adjusters and locknuts are replaced into the frame cavities & engaging the swing arm, the allen wrench opening adjusters (pivot pins) need to be adjusted. If you did not move their locknuts originally except perhaps 1/2 turn, or 1 turn, as needed to just loosen them, it will be a bit quicker. In any case, what you must do is screw both adjusters inward with an Allen wrench, as evenly as you can on each side. View the space between swing arm and frame, to eye-ball the 'even-ness'. DO NOT try to really tighten them much, light to moderate finger tightness is all that is needed and desired. Try to keep the swing arm roughly centered in the frame. You can use a selected small allen wrench from the BMW on-bike tool kit, or a selected diameter of drill shank as a thickness gauge, placed between the FRAME and the SWING ARM, to measure the centering of the swing arm in the frame. This may take a few attempts until the swing arm is centered; that is, the selected size of drill shank or allen wrench inserted between frame and swing arm shows the same spacing, side to side. Loosen one pivot bolt, tighten a wee bit the other, until things are close. When equal, use your torque wrench, and you want 7-1/2 footpounds of torque on the adjusters AT THIS POINT OF THE PROCEDURE. Play until the swing arm is centered, with 7-1/2 footpounds. Assuming that you now have equalization of spacing, torque ONE of these pivot adjusters to 15 footpounds. THEN, back off a bit, and re-torque to 7-1/2 foot pounds, stopping at 7-1/2 whilst going in the clockwise tightening direction. If the spacing is now still fairly equal, fine, if not, back off one adjuster, tighten the other, in the same manner, & repeat until near perfect. In BOTH INSTANCES, the pins are to be tightened to 15, then backed off and retightened to 7-1/2. LASTLY, tighten the 27 mm thin steel nuts with your modified socket & torque wrench to 70 to 75 foot pounds. Some folks paint-mark the end of adjusters-to-nut to be sure that they have not moved while the 27 mm nut is being tightened, usually they do not move. There is nothing super-critical about equal spacing. If you are within maybe .020", that is quite good enough. The original purpose of the 15, then 7-1/2, was so if the bearings were freshly greased, then the 15 made sure the grease was squeezed to proper thickness. You don't want to leave the pins at 15, because that does warp the frame/swingarm...hence use the 7-1/2 factory specification as the final adjustment. The 15 and the 7-1/2 torquing feeling is not dead solid, but feels like something is giving a bit.
NOTE!!....To be sure there is NO confusion here; there will be NO feelable side to side freeplay in the swing arm to frame mounting when you have adjusted the pivot adjusters properly. You are taking up all free play, equally spacing the swing arm in the frame (side to side), & then leaving the adjustors with some torque on them, specified at 7-1/2 footpounds, AFTER first torquing to 15 footpounds, backing off, & resetting to 7-1/2 IN THE TIGHTENING DIRECTION. Obviously, setting one side presses the swing arm against the other side, so you can't do both at the same time together. You do the centering adjustment, bring the pivot adjusters close to correctness & then adjust ONE side for proper torque & see if the other side & the first side match in spacing. After you have done this once, you will find it very easy. Use your torque wrench with the Allen adaptor of 6 mm size, the other end the square drive to match your torque wrench.
NOTE!! I grease my swing arm pivot/bearings roughly twice a year, depending on my traveling conditions and mileage. I grease both sides with my pointy-tipped grease gun with the tapered rubber tip (common item, NAPA stores or chainsaw stores for the grease gun part). Every 4 to 6 years I pull the entire rear structure backwards enough to hand-clean & eyeball inspect & finger-feel the condition of the swingarm bearings. When doing the final greasing, through the allen hole with my rubber-tipped grease gun, I use a quite goodly amount of grease & then I use my fingertip to wipe the excess grease, all-around, to smooth coverage at the junction of swing arm and frame. Making this clear, the grease is left, that spacing area is full of grease, but smoothed, in the area between the frame inside surface & the swing arm inside surface. That way, any water getting in the area will see a layer of grease in that 'cavity' for which you set the equality distance. I prefer the NON-sealed bearings, so all this greasing works properly. If I have a sealed bearing I am installing, I may destroy/remove the seal first ON PURPOSE. Late models may have sealed swing swing arm bearings....I have seen earlier models with this type & with an intact seal you have to go about greasing things differently, perhaps with a sharp grease needle from the side, through the seal, etc. I prefer UNsealed bearings, with a lot of grease, smoothly done in the mentioned space. I mentioned the early style seal used with the standard open bearings, earlier in this article and see the next paragraph. If you want to use sealed bearings, that is OK, but up to YOU. The bearing is the same type and size as used on the PRE-1985 wheel bearings....type 30203, a very common part.
Re-greasing during every year with a grease gun and rubber tip, through the allen pin will insure you have forced contaminated grease out of the bearing, at least fairly well.
The R45/R65 models came without one spacer & grease containment item.
13. If not already done, I add a wee dab of moly grease to the working end of the clutch arm where it fits against the rod in the transmission and re-install the clutch arm and associated parts. Note that I, as mentioned previously, have also put a small amount on the tip of the rod at the front before the transmission is pushed forward.
14. Clutch Adjustment: see http://bmwmotorcycletech.info/clutch.htm
©Copyright, 2013, R. Fleischer
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Last check/edit: Friday, August 05, 2016