Servicing Transmission input (clutch) splines, throwout bearing &
clutch arm. Early swing arm bearing seal rings.
Including cleaning, lubrication and inspection, etc)
Includes information on swing arm locknuts, adjusters, and how to adjust those items
article #43 inputsplinesthrowout.htm
© Copyright, 2014, R. Fleischer
I recommend you read the clutch article: http://bmwmotorcycletech.info/clutch.htm
I thought about combining these two articles, but felt 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 have not only splines at the input of the transmission, but have
splines at the driveshaft output area...that is, the rear drive input. THOSE are easy to get to.
ALL MUST be kept lubricated.
Skill level: For input splines on Airheads...lower intermediate or better; for K-bikes, for rear drive/rear of
driveshaft splines, skill level is same. For K-bikes input splines, skill level: lightly advanced. For the throwout
bearings & clutch arm servicing of all these bikes, moderate skills needed.
GREASE: 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:
NOTE: The 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
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 the entire transmission must be overhauled & re-shimmed. The clutch splines
(transmission input shaft splines as you should probably NEVER 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 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 large expanded sketch, so I am
not doing it here.
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.
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 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, the suddenly large forces try to spit out the grease from the wheel cup splines. Since the torque is
huge here & 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 possibly be a very nastily thick TAR, but that
would keep you from being able to remove the wheel for tire service!
Whenever you clean & grease your Airhead's input splines, ALSO do the throwout bearing service. Take
out the parts (VERY easy to do), inspect them & pack the bearing with a light smooth grease before
reassembly. Greasing gives some lubrication before the transmission oil slowly works its way to the bearing.
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. Sometimes, yes, sometimes
NO. 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 12,000
miles since the last lubrication (& if unknown, do it NOW!). If OK, go to 18,000; I doubt you will be able to go
much over 24,000 miles, no matter the type of shaft, plated or not. 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% seems adequate) 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
Throwout bearing: see the Clutch article: http://bmwmotorcycletech.info/clutch.htm
What follows is a step by step HOW-TO article ON 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, 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 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 as appropriate with a
standard extension; 6 mm allen wrench in 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 or yardstick, etc., and a few minor items you
are very likely to have. It is handy to have a MODIFIED jack: http://bmwmotorcycletech.info/hydraulicjack.htm.
The tools above 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, which is more work, as you may have to remove the
driveshaft housing, shock absorbers, battery tray, etc. There is no question that a total removal allows a much
better over-all job. A total removal of the transmission is not difficult. 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.
I do recommend a full removal at least every 60,000 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 too).
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 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 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
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 at:
Click your mouse on the left side at Technical Tips. Read the articles on the throwout bearing by Matt
Parkhouse, dated 12/99; and mine, on Lubing the Transmission/Clutch Splines, ORIGINALLY dated
12/04. 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 basic 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, said
groove has 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 then 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 the 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, latest version had needle bearings. Some have modified the Airhead arms...&
the K-bike arms, for grease passageways and a zerk. I consider it more of 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...and you can try a bit of heat and cooling to suck in some
oil...sometimes that works on really frozen up ones. I usually use a bit of heat on the arm and then
soak the warmed arm needle bearing area in a light solvent, and later I clean that out, and try to get
the needles to be movable...and grease them. 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 bearing had BALL bearings, The later not-as-good style had a
flat radial needle/roller bearing, and after 9/80 it is a ball bearing again (maybe). There is some
variance in the outer spring and 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 and 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
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 the input splines greasing, with the
clutch lever removed. In fact, without the lever removed, you probably can not do the splines
properly. 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 airbox and airfilter. 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...and you CAN do that now. With the starter cover off, it is a great time to
check the nuts on the electrical post of the starter. Best to have ALL the wires at the negative post of
the battery disconnected if removing the starter cover. If you've have had 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 (not on early 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.
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 that 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....OR?? it is easy
If you decide to remove the transmission, unfasten the driveshaft U-joint from the transmission, remove
the swing arm adjusters.....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 is used on the threads).
If you have the rectangular airbox, remove the 13 mm hex headed bolt that goes straight down through
the top of the airbox, middle, of 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. 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. HINT! Some folks have a hard time removing and replacing the plastic input tubes to the
carburetors. On some models, these tubes are not the same, left to right, and also ARE NOT
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, it is FAR easier 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, that rectangular box), the whole assembly lifts off easily, and replaces more
easily. 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.
8. Using the Chinese jack from my article as modified, 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 with the nut still attached. You may have to wiggle the tire/swing arm a bit to
allow the adjusters to be removed, and that helps avoid damaging the threads. I have seen these not
lubricated properly and rusted badly. I have seen the bearings rusted bad enough to crack! If yours
are bad, I recommend you remove the entire rear end of the bike and service the swing arm bearing
area. Various puller styles will work to remove the outer bearing race, Ed Korn
(see http://bmwmotorcycletech.info/tools.htm article) made a cute one, and in a kit to 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.
9. There is sometimes no need to undo any shift linkage for just a spline re-lubrication. You
DO have to
undo the wing-nut on the rear brake rod, if you have a drear drum brake.
10. Pull rearward on the transmission. It will likely come backwards a wee 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, 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:
Some of the old BMW Factory Service Manuals did call out using a piece of wood to
keep the rear end moved rearwards. In fact, they specified it for when removing the
transmission. I am NOT speaking here of using a piece of wood between transmission
and engine; which is not absolutely necessary, certainly not with this other piece of
In my only copy that specifies the size, BMW said to use a 20 x 400 mm piece of WOOD,
placed between the TIRE and the rear section of the FRAME. This DOES WORK, but
you will almost certainly have to find out what the wood wedging piece thickness
will need to be for YOUR bike, as it is not the same for all years and models, and, of
course, tire sizes.
NOTE! It is not uncommon for someone to complain that the transmission will not move backwards much.
See #9, just above!! Rear brake tight?....if so, undo the wing nut.
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 fully that input shaft end I mentioned
just above of the transmission input spline. It is nice to be able to get the center rod to the rear 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 breath 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!). If the splined center of the clutch disc is very greasy, clean with a rag. DO NOT SPRAY
SOLVENT ON THE DISC SPLINES.
To both clean and grease the transmission shaft input splines, I make up TWO simple tools:
Use two common "acid brushes". 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.
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 along the INPUT spline; that is, the TRANSMISSION 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
the INPUT spline by spraying a good cleaner on it, but remember, do NOT clean the spline of the disc!...except
to poke & wipe with tiny rag pieces if need be (You CAN use a TINY bit of solvent on those tiny rags). If you
spray solvent into the clutch disc splines, that can easily 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; or, Berryman B12 carburetor and choke cleaner in the
spray can, with a spray wand, is good!! ON TRANSMISSION SPLINES.
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. The felt is
used on earlier models. It is easier to install 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.
Grease the INPUT SHAFT splines once the solvent is totally evaporated. Work the grease into the splines, bit
by bit, all around, using the greasing brush tool. It is not needed, nor desirable, for too much grease.
If the rod END that is in the center of the input shaft is not visible, make it visible. This is usually easy with the
clutch lever having been removed at the rear. Put ONE SMALL drop of 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 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 keeping 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. AGAIN: 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
that bolt and washer?). The clam shell model requires the right clam shell to be in place for this. Do
NOT forget the grounding wire. 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, these
adjusters (pivot bolts) need to be adjusted. If you did not move the 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, a bit and as evenly as you can on each side.
DO NOT try to really tighten them much. 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, using them as a thickness gauge, placed between the FRAME and the SWING ARM, to get the
swing arm centered 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.
DO NOT USE MUCH FORCE.
What you will then do is torque one of these pivot adjusters to 15 ftlbs, back off a bit, 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 fairly equal, fine, if not, back off one adjuster, tighten the other, in the same manner, and repeat
until near perfect, then tighten the 27 mm thin steel nuts with your modified socket and torque wrench to
70 to 75 foot pounds. Some folks paint mark the end of adjusters 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 good enough.
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 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.
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 few years I pull the entire rear
structure backwards enough to hand-clean & eyeball inspect & finger-feel the condition of the
bearings. You can also use a chain saw grease gun with pointy tip. At one time there was a
BMW 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. Making this clear, the grease is 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 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.
Every few years it is not a bad idea to remove the swing arm...or move it backwards...enough to
do a thorough bearing service. As noted, I like to leave enough grease in the measured space
area that rain, washing, etc. does not get in there. As mentioned, a sealed bearing is not needed.
In fact, the R45/R65 models came without one spacer & grease containment item. Again, as
mentioned, if I find the bearing sealed, I usually prick or otherwise actually on purpose damage
the seal, so greasing goes to the proper areas. The bearing is the same type and size as used
on the PRE-1985 wheel bearings....type 30203, a very common part.
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
01-15-2003: Clarify & add to tools list; add applicability & skill level; add reference note on 50,45, 40 mm
01-22-2003: Add section on adjusting the swing arm, and modify here and there to incorporate clarity for
that, add hyperlink within the page for that adjustment. Add #13.
04-16-2003: add .htm title; clarify many details.
05/06/2003: add note on ball type throwout bearing seen on 1984; note to coat the 13 mm bolt's
WASHER in top of transmission; typos; input seal note in #10; clarifications
05/11/2003: rework #12, to eliminate one reported incident of someone managing to jam something or
05/15/2003: correct typo, 1-1/6" should be 1-1/16".
07/26/2003: expand #13, add ref to #3, and add #14
08/28/2003: add #15.
11/21/2004: remove #15, back into #13, and references to #3 added as necessary.
06/01/2005: bearing number added
07/10/2005: updated to eliminate some confusion in procedure
07/11/2005: additional small changes on adjusting swing arm, and about the seals there
07/23/2007: Some editing for clarity
11/04/2008: In item 13, change part number of pin from 23-21-1-241-484 to proper 23-13-1-241-484
12/05/2008: Update item 12 for clarity.
08/31/2009: minor clarifications
10/27/2009: Clarify a lot more details
10/28/2009: Add wing-nut information, #9, #10.
06/24/2010: Add information on why fine and not coarse splines at the input shaft, clean up article a bit
(not a thorough job)
07/02/2010: Corrected minor typos, clean up article, add notations to clarify about K bikes, other minor
05/16/2011: fix typo in #12
10/13/2011: minor for clarity
10/19/2011: Do a bit more re-arranging, etc., for clarity
11/16/2011: Removed discussion on specific greases, and refer to my extensive article #73.
04/08/2012: Clarify details on throw-out bearings, and a few more minor points elsewhere's.
06/08/2012: Completely re-write #14, and add note at top recommending reading the Clutch.htm article
06/28/2012: Re-do clutch adjustment section to agree with the just updated similar section in
10/06/2012: Add QR code; add language button; update Google Ad-sense code; fix some typos, clarify a
04/28/2013: Shorten article by using references to Clutch article. Clarify more details, clean up, etc.
09/22/2014: Minor cleanup, nothing of importance technically. A bit more on 08/22/2015 and 8/24 (hints).
11/29/2015: Finish cleanup and meta code changes. Add note about the seal rings. Adjust spacing so
most of article is to left side.
© Copyright, 2014, R. Fleischer
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