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Servicing Transmission input (clutch) splines,
 throwout bearing and clutch arm.
(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!  HYPERLINK: 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 and 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 inut of the transmission, but have splines at the driveshaft output area...that is, the rear drive input.  THOSE are easy to get to. They 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: advanced.  For the throwout bearings and 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, please see
chemicalsetc.htm 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.
 


Background information:

Besides avoiding SPLINE WEAR from rusting, and helping with such as fretting corrosion; cleaning and re-lubrication of the transmission input shaft splines will make operation of the clutch smoother, and shifting easier.  If kept properly lubricated, the splines may last almost forever; good because replacing an input shaft is expensive.   The clutch splines (really I mean the transmission input shaft splines as you NEVER grease the clutch disc splines, although they work with each other)... are fine toothed, and the teeth not deep, and dryness and rusting (or what appears to be rusting) causes problems. The normal use of the clutch causes the clutch disc splines to slide back and forth along the transmission input shaft splines, wiping away the grease. The grease will go away after some mileage; and rusting and other serious wear 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 and without molybdenum disulfide, which is usually just called MOLY). If the clutch splines wear enough, you will hear a very uncomfortable noise, and 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? AND...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 and numerous splines (and 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, and 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, and 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 and 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 and female teeth is increased from the rather tight; that is barely-able-to-be-assembled-with-oil point, to a nice smooth fit;....and 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, and 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 and off, and 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 and cold changes, and some quite (one hopes!) goodly protection against effects of humidity and 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 sudden and large forces try to spit out the grease from the wheel cup splines.    Since the torque is huge here, but 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 work to 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!


 NOTE!....whenever you clean and grease your Airhead's input splines, ALSO do the throwout bearing service. ...at least take out the parts (VERY easy to do) and inspect them, pack with a light smooth grease before reassembly.  The greasing is done to give some lubrication before the transmission oil 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 and 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 (and if unknown, do it NOW!!!), and if OK, go to 18,000; I doubt you will be able to go 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 30,000 miles. Those that do shorter rides, shifting a lot, in wet climates, ESPECIALLY if engine cool-down is in a high humidity area, 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 rusting at the shaft, unless the grease is still intact. In fact, this condensed moisture can actually promote washing-out of the grease.  For smooth operation I prefer quite a bit of moly in the grease (about 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 my chemicals,etc.htm article.


Throwout bearing: see the Clutch article: CLICK!


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, and 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 Chinese bottle jack, an article on that modification is on this website...and that WAS a hyperlink, although it is listed on the Tech Index page as item #66.   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, shock absorbers, battery tray, etc...or do it how I show it below.  Do NOT overly grease the input shaft.  Follow directions!  A total removal of the transmission is not difficult, and you gain access to do a very thorough cleaning and re-lubing, checking condition, etc., of the swing arm bearings, and you get into other areas for inspection.  YOUR choice.  I do recommend doing the removal and full checking of everything, at least every 4 to 6 years.
 

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.

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 clutch 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:
     http://www.airheads.org
     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 CLUTCH 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:   clutch

      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.  
     
      oilsketch.htm has all the breather information, well down that page.

6.  Remove what vacuum and smog parts, if any, that you need to on your particular bike (you may want to
     modify at this time or before re-assembly).  Remove the left lower bolt on the transmission, and the
     right lower bolt.  NOTE the brown grounding wire at the left lower bolt if you have that.  Pay
     attention to washers.  Remove the left upper bolt.  Remove the nut on the right upper STUD. 

     SOME folks may want to fully remove the transmission:
     I suggest you add a nut to the upper right stud, lock the 2 nuts together, and thus remove that
     stud.   You may want to consider changing that stud to a bolt. The twin nut is fine, can be left
     in place that way, and you don't REALLY have to remove the stud...for the SPLINE service. 
     Removing the stud on some  models makes removing the transmission and other servicing a
     bit easier, and then USUALLY the battery and battery box need NOT be removed. Your choice
     here.  The only disadvantage of the stud is lining up the transmission input splines to the
     clutch disc, and maybe if some ham-fisted person tries to install the transmission on a nasty
     angle...UNlikely though.

     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 and 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 a metric size vacuum line crossover hose and for the gas line crossover hose that pass through the area.  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 /5, and want to keep it original, you can get the original silver braded fuel hose from Bing Agency or VW dealerships. I don't think it is as good as the later black BMW metric fuel hose, particularly for life.

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 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.

****NOTE!  It is not uncommon for someone to complain that the transmission will not move backwards much.  See #9, just above!!  The rear brake is tight?....if so, undo the wing nut.

****NOTE!   If you see an OILY spline at the transmission and see oil coming from the input end of the transmission, you MUST undo the universal joint, remove the transmission entirely, and replace the transmission input seal.  Failure to do that 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.  

 Some may prefer to totally remove the transmission, and clean the area at the clutch and transmission, check for leaking oil pump seal, leaking main seal, etc.  NOT mandatory unless you see leaks.

Ideally, the transmission, when in the bike, is 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
allow 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:

Take 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 tie securely those brushes to some sort of thin rods 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, 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, and move the brush back and 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 and 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 and wipe with a rag if need be.   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!!

IF that area shows OIL leakage from the transmission, remove the transmission and replace that seal...and ask the LIST or check my transmission article on how to do that!  It is not difficult and 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 that 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, and 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 and 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.

12A.  Reassemble everything, bit by bit, slowly, and carefully.   Do NOT allow foreign matter to interfere
         with the transmission coming up to the engine cleanly, and squarely, and fully.  Be sure the
         transmission is fitting squarely
,  and then cinch up the bolts, evenly, in a cross pattern.  Do not forget
         the vertical 13 mm bolt (you HAVE used a 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 and the clutch lever at the rear....and do any cleaning and
         lubrication there that you did not do previously.

12B.  Centralizing and adjusting the rear swing arm:

    After the adjusters and locknuts are replaced into the frame cavities and 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 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 the equality of the spacing.  If you are within maybe .020", that is good enough.  

NOTE!!....just 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), and then leaving the adjustors with some torque on them, specified at 7-1/2 footpounds, AFTER first torquing to 15 footpounds, backing off, and resetting to 7-1/2.  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, and then adjust ONE side for proper torque, and see if the other side and the first side
 match in DISTANCE.   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).    Every few years I pull the entire rear structure backwards enough to hand-clean and
eyeball inspect, and 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 quite a goodly amount of grease, and then I use my fingertip to wipe the excess grease, all-around, down to smooth coverage. Making this clear, the grease is in the area between the frame inside surface and 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 arm bearings....I have seen earlier models with this type and with an intact seal you have to go about greasing things differently....like 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.

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 and 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 CLUTCH article


  Revisions:
01-15-2003:  Clarify & add to tools list; add applicability & skill level; add reference note on 50,45, 40 mm
                    bolts.
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
                    other.  How???
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
                     stuff.
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
                     CLUTCH.HTM
10/06/2012:  Add QR code; add language button; update Google Ad-sense code; fix some typos, clarify a
                     few details.  Language button removed in 2013, due to javascript problems.
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.

Copyright, 2014, R. Fleischer

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