Applicability: All BMW Airhead models; with some useful information for any splines-driven dry-plate clutch.

Why do it: (1) Smoother shifting; (2) Avoid wearing out expensive parts with expensive labor to repair damage; (3) Avoid sudden spline failure

When to do it: Depends on year model and conditions you ride in, but probably every 12000 to 30000 miles, and probably every few years if you do not ride much.

What are you going to do: Unfasten the transmission, move it slightly backwards, clean and lubricate the transmission input shaft splines, and then reinstall transmission. You will probably do other work at the same time, described in the text that follows.

NOTE:  While an adequate job can be done by just moving the transmission backwards, a 100% job means removing the transmission from the motorcycle.  That can usually be put off until you have another reason for removing the transmission.

Required Skill level: Lower intermediate or better

Tools and Parts needed:
Standard owners BMW on-bike tool kit
Torque wrench with drive adapters including 6 mm allen wrench
Modified 27 mm or 1-1/16th inch socket (see text)
Cleaners and lubricants (see text)
Means of tying front end to floor (see text)
17 mm wrench and 15/16 inch flare nut wrench, or substitutes, if you have the smog pipes (Pulse Air System) at the aircleaner box.
13 mm box-end wrench
6 mm L-type allen wrench, possibly shortened
Two “acid” brushes with piece of rod or dowel to extend their length using duct tape or?
A couple of small pieces of “one inch” wood, or perhaps a piece of 2×4.
Possibly a light duty floor jack and possibly a modified ‘Chinese’ jack (see text)
Possibly a 07-11-9-918-655 allen head bolt with captive washer (one) (once only)
Optional, if totally removing transmission:  Adaptor for torque wrench to anable torquing of the U-joint 4 bolts.  See tools article on author’s website.

Preface and Notes:

I was unable to do a reasonably sized article that covered every model in minute detail in a step-by-step format. I would have preferred to have available a /5 and a mid 1990’s model with the additional smog components and the change in the muffler system, but this was not to be, so I decided to do this article with readily available bikes, a 1983 R100RT and a similar 1984, which are certainly good enough for these purposes, as much of the procedure is similar for all models, and differences are easily seen and accommodated.

The “clutch splines” (in actuality we are going to be lubricating the transmission input shaft splines) should be cleaned and relubricated BEFORE they show signs of rust, as rusting means wear is occurring. Over many years and with many different BMW Airheads, I have found that 20,000 miles (20K) was not quite soon enough on most Airheads, and I began regreasing every 15K. BMW supposedly nickel plated the transmission input splines on models from 1985 or so, these may (or may not!) go the published 30K between lubrication per BMW. Certainly there is less tendency for rusting. Short trips, and high humidity where you ride or store the bike after riding, means it will be more likely you are going to need to do this procedure at less than 30K on the plated splines and less than 20K on the unplated splines. This is due to moisture condensation as the engine cools. Many factors are involved, including the number of engine heat-cool cycles, very short trips, how often you use the clutch, etc.

**I suggest that you place a copy of this procedure in your computer, print it, make notes on that as you do this procedure, and then modify the original for your specific bike. Then you will have a printable copy for your second and subsequent spline jobs.

**If you have never done this cleaning and lubrication before, BE SURE to read this entire procedure completely through, at least twice. Allow yourself 6 to 8 hours for the first time. You will be figuring out how to, for YOUR bike, jack up the rear end (or not), or tie the front wheel to the floor (or not)….and there will or could be minor complications with your specific model.   So you will have some thinking time, not to mention you will be wanting to go slow the first time. This will all finally end up FAR simpler than it may appear from a first reading here. The second and subsequent times you should be able to do this procedure in 2 hours +-, depending somewhat on your attention span, number of donuts and coffee breaks, and the model and equipment.

Don’t do wrenching on your bike while drinking alcoholic beverages!

1. IF you find you need to do it, find some method of getting the rear wheel off the floor, about an inch is adequate. Do some experimenting and some thinking. If you are a really high mileage rider, you might want to make up something convenient and easy to use, such as a special lift stand, or floor jack with fitting spacers, etc. It really depends on your model and how YOU want to do things.

Try this idea: lift the rear end a bit and slide a thin piece of wood under the rear tire, enough to put the front tire on the floor and then tie the front end to the floor. At my home shop I use two screw female studs that were installed into the concrete floor, with a homemade padded omega-shaped clamp that fits through the bottom of the front wheel. Some folks use a jack and a 2 x 4 under the exhaust pipes just in front of the rear wheel….lots of ways to take the weight off the rear end, have the tire slightly off the floor.   If you have a ride-off stand, you will likely have both wheels on the ground already, and you may want to put an inch thick piece of plywood, or?, under the CENTERstand.

During the procedure for the actual pulling rearwards of the transmission, you need some method of keeping the transmission towards the rear, with either wood wedges, or something else.   One particularly good method you might consider, that pretty much obviates any need for wood wedges and then cleaning out any wood fibers from the transmission-to-engine joining area (NOTHING must be in that joint area, not even dirt, or the transmission will not bolt back to the engine fully, squarely, evenly), is to have a ring (or?) mounted to the rear wall of your garage, using that with a bungee cord to keep the rear wheel fairly well pulled towards the rear after undoing the swing arm adjusters.   Out on someone’s driveway, I have used bungees from the rear shocks to a rear rack on the motorcycle for the same purpose.

Please keep in mind that you should devote a fair amount of energy and time into just how you intend to do this job, modifying along the way if you have to, as this greasing procedure is something you will be doing regularly, and, as you can figure out YOUR method, write it down, perhaps in YOUR copy of this procedure.

This procedure assumes you have unscrewed and removed (or are going to) the swing arm adjusters and are pulling the swing arm to the rear slightly, but that is not always necessary on all models; but you are likely to want to do it anyway for the extra clearance; that is, different models have differing amounts of room between the rear of the transmission and the swing arm. What IS necessary is to have the transmission pulled rearward enough to expose the forward edge of the input shaft; or preferably a bit more.   If there are considerable miles on your bike, and you have never done it, you might consider unfastening the shock absorber(s) and removing the bolts on the transmission output flange, disconnecting the mechanical brake, ETC., and pulling the swing arm either out, or rearwards enough to allow a FULL cleaning, inspection, and lubrication, of the swing arm pivot bearings.  Those are almost universally never removed for true servicing, and many rust badly, and the bearings fail.

Once you have the bike secure and the rear wheel off the floor, you are ready to proceed. Keep in mind that you likely will not have to do many of these following steps; or, find you may have to add some few minor items.

2. Disconnect all battery negative terminal leads. Remove the airfilter cover and airfilter. If you have the early clamshell type of aircleaner housing, there is a long bolt with a slotted head on the left side. Once the bolt is removed, PULL the LEFT clamshell straight out to the left, it is stiffly held by a metal spring clip at the bottom, hidden inside.

***NOTE: when I do this procedure I take the extra steps of disconnecting the fuel hoses from fuel tank, and fuel tank overflow and any other hoses under the fuel tank, and I remove the tank. You may well be able to do this procedure without doing that, but I really suggest that you do remove the tank…and do tank cleaning and electrical connection servicing, ETC., while the tank is off.  Remove and clean/spray with contact cleaner (and silicone greasing) the plugs and connectors (ESPECIALLY the starter relay). Check routing of control cables, and generally eyeball everything. If you have a 1981+ model without the rivets at the ignition module of the last models, clean and recoat the underside of the electronic ignition module with fresh silicone heat-sink compound. While you do not have to remove the battery on some models, I suggest removing the 10 mm nuts and washers from the TOP REAR of the battery carrier and the battery cables…and push the top of that carrier to the rear..and remove the battery…good time to load test it, see water level when not tilted (flooded type batteries), etc. You may or may not need to deal with some aspects of the battery and its carrier. On some models some of these things can be avoided in the future with an easy modification, described later on, to the upper right stud coming out of the engine that the transmission and airbox bolt to.

***Consider removing the starter motor cover, as while this is a great time to inspect everything under the gas tank as was just mentioned, plus such as the ignition coils for carbon paths on the tower outsides, and corrosion in the towers, and perhaps ohmmeter tests, it is also now easy to check the starter connections for tightness. Consider making this greasing procedure part of your regular inspection of the timing chest…particularly if you have the awful stock rubber diode board mounts. If you are going to replace the diode mounts you need the starter motor cavity access, and if they are bad, isn’t it nice that you have things apart right now!   I HIGHLY recommend replacing rubber diode board mounts with aftermarket metal ones. It solves several problems, electrical and mechanical.   They are available from:
http://www.thunderchild-design.com/homepage.html and http://www.euromotoelectrics.com and from www.Motoelekt.com.  It makes little difference if you get metal mounts that are hex, or round, or finned.

3. There are circular band-clamps for each carburetor and carburetor hoses and airbox adaptors. I have found it possible to do this procedure in most instances WITHOUT removing the carburetors or carburetor cables. That avoids re-synchronizing the carburetors. I suggest you loosen the three carburetor clamps only on the airbox side for both carburetors. You will need to separate the airbox adaptors from the airbox. On my 1983 and 1984 bikes used for this article, only the rubber hose adaptors, and not the plastic adaptors, needed to be pushed down a bit at the aircleaner housing.

This is a great time to decide if you want to remove the Pulse-Air system (DO NOT modify or remove the oil breather system), or the fuel fumes system on the last versions of the Airhead. There are articles on how to do this on this website and the author’s website…SEE BOTH of them.    The Author’s website is:  https://bmwmotorcycletech.info/index.html
specific article is the PULSE AIR article, which is #11.

If you DO have Pulse-Air system emissions tubes you will need to loosen the nuts (17 mm flare-nut wrench is best) to remove the tubes from the aircleaner housing, left and right. Exactly what you remove depends on if you are removing and plugging the system, and how you go about it, or if you are simply removing enough to service the splines, the point of this article you are reading.  Inside the air cleaner housing you will have to wiggle the T-tube fitting out of the portion going forward, and then remove the entire assembly (T-tube, rubber tubes, plastic parts in carburetor feed). If you have already removed all the emissions garbage, you likely will only have to pull the plastic T fitting rearward out of the rubber hose that fits into the forward aircleaner box wall, and push that hose forward out of the airbox. Your particular setup may vary a bit.

Don’t mix up breather and Pulse-Air parts/systems in your mind. The breather system is the large hose system that attaches to a casting cover in the starter motor area. It can be, in the aircleaner area, one or two hoses to one or two carburetor intakes…depending on model and year. All airheads use some sort of breather system.

4. Remove the upper right transmission nut and thick washer from the stud. That stud is sometimes sealed by a Loctite-type product to the engine and need not be removed. If you want to remove it, the easiest method seems to be to attach two nuts engaging full nut threads, tighten the nuts to each other, and use these to rotate the stud outwards. Some folks will find it VERY convenient to replace this stud with a bolt, you MAY find find out the reasoning for this when you get farther into this procedure; or, just look at how that airbox is to be removed…with the STUD it has to be moved very far rearward, and the battery and likely the battery carrier, removed (or, at least the battery carrier lifted up after undoing all 4 of the 10 mm battery rubber mount nuts). If the stud is replaced with a bolt (on some models), the battery and carrier can be left intact. This is especially helpful for those having Luftmeister side tanks, and they must normally remove the right side one to enable getting to the nut that holds the rear disk brake reservoir and battery carrier.

***Note: In the engine casting, the top right stud hole, and the top left bolt hole, and the left lower bolt hole; are NOT drilled completely through into the engine. Further, BMW has not held the depth of this drilling (and threading depth) to any tight tolerance. Because of this, always use the bolts and washers (some are thick) that are correct to fit in the respective places. IF you are going to install a bolt at the upper right, I have found that a M8 x 50 allen headed bolt, with captive flat washer, part number 07-11-9-918-655 seems correct, but sometimes you have to add the original thick washer. You could always grind down the bolt a bit, clean up the threads of course, and then avoid an extra washer (all, IF needed). You do not want the bolt to bottom in the threaded hole before it clamps FULLY on the aircleaner housing and transmission…and, of course, you want a fair amount of threads in use too. It may be that the bolt will actually be OK in length. You should check this.

CAVEAT: Although it may seem that there no downside to changing that stud to a bolt (which may eliminate any need to removing the battery and tray), there are some considerations. The stock stud is of such length that it allows the transmission to be moved back the 3/4 inch or bit more that is needed to allow the cleaning and regreasing, without the transmission going downwards, possibly injuring the neutral switch. The stud also makes it a slight bit easier in reinstalling the transmission at any time. Frankly, I would vastly more prefer to have the bolt, not the stud, and simply put a block of wood under the transmission and protect the neutral switch. If you look underneath, you will see that this is usually not a situation for any special concern, it is being mentioned here so you get 100% of the facts.

NOTE: All four transmission-to-engine bolts should always be cleaned and have a SMALL amount of antiseize compound put on the threads. Theoretically BMW bolts (the older ones at least) are cadmium plated and do not need antiseize compound. That is not so on later and replacement bolts.    I prefer using a faint amount of antiseize on all these bolts/studs, as it also eliminates any potential corrosion. At a minimum, CLEAN the threads.

5. Remove the top left transmission bolt and washer. If not already done, push air breather hose where the center T section pushed into…to front, so no longer gripping the hole in the front of the airbox. The clam-shell air cleaner housing setup is a bit different, easy to see what to do. Lift or move parts to side..you may have little or many parts here.

Remove the 13 mm bolt in center going down into the transmission on the rectangular aircleaner model. On the clamshell models, this goes through the spring clip, and is left alone, unless it has been leaking. It is this 13 mm bolt that is thread sealed (I use NON-hardening Permatex Form-a-Gasket type #2) upon reassembly to avoid transmission oil being sucked-up past the threads.  A washer is used, goop it on both sides too.

I suggest you make notes of where the fuel lines and vacuum and breather lines and such were routed.

If the starter cover has too tight a fit, you can consider relieving its metal SLIGHTLY as needed.

6. Remove the entire airbox. As stated previously, in order to do this you might have to remove the battery, and even the carrier may need to be lifted up and to the rear. Some folks have the upper two subframe bolts to disconnect, if the battery is not removable in the forward direction. Those with the easier to remove Panasonic and similar smaller width AGM/VRLA batteries have fewer problems. When you look at your bike, and see what is in the way to moving the transmission rearward ~ an inch, you will see what I meant, above, about the upper right stud.

7. With a a 6 mm Allen, short leg being shortened if need be, remove the left lower transmission bolt. I keep my modified 6 mm allen wrench as THE one in the bike tool tray. Note the brown grounding wire/lug under the left lower bolt, and do not forget to replace it when reassembling the bike.

8. Remove the right lower bolt/nut. Note that in many cases, you can leave the clutch cable and clutch lever IN PLACE (but watch that lever and its ears mounting, don’t allow any damage). This is a very good time to REMOVE and clean and lubricate the clutch lever, and INSPECT and lubricate the throwout bearing parts. Early levers had zerks, later ones had a needle bearing that needs, sometimes, to be soaked in thin penetrating oil or solvent, cleaned, and then soaked in heavier oil.  To ensure a good oiling of that later type of lever, I soak and clean it in warm kerosene, dry it, then heat it a bit, then add oil to the bearing, then add a few more drops of oil as the lever cools off.   If you have the C clip type of pin that holds the clutch lever (that C clip is located on the INside top of the LOWER ear), you must be exceedingly careful when replacing it, as if the C clip ever comes out, the pin can move out of an ear, and you can bust an ear off the rear of the transmission upon the next clutch use. BMW offers a modified pin with a top-hat.  23-13-1-241-484 with clip 51-23-1-864-963.  I recommend you remove the troubleshome C clip parts and use the modified pin with a top hat or a bolt and nut. The /5 used a cotter key for its fastening, which is very good, but after a few uses, it must be replaced, but cotter keys are common and very cheap. If you have a cotter, be sure to bend over at least one cotter leg. Most cotter keys can be reused once by not bending over both prongs, only one, to begin with, then on next time you do the job, bend the other one.

In some instances, model year dependent,  it may be nice to modify the RIGHT LOWER transmission FINS a bit, for ease in removing and reinstalling that right lower bolt. If you file away fins a bit, do it smoothly.

9. You might NOT have to do this step (I didn’t on the 1983 and 1984 RT): Remove bolt from left footpeg at frame, leave shift linkage attached and lay assembly out of the way.

10. Remove swingarm round plastic dustcaps. Loosen, about 1/8th turn, the locknuts on both sides of the swing arm…use a modified 27 mm or 1-1/16″ socket. (If you HAVE TO, you can use the BMW special wrench, modified, but it is NOT overly strong). The end of your 27 mm or 1-1/16th inch socket should be lathe-modified or just ground flat and square so there is no internal taper relief left. Also grind the circumference of the socket as needed, to be sure that the socket seats fully on the nut, fully through the innermost of the 2 internal diameters of the frame, look with a flashlight, you will see what I mean. Doing this grinding or lathe work will ensure your socket fits all the way inwards, AND, won’t round the thin nut edges easily. Hand grinding is OK, but is BEST to use a lathe for that and squaring the end. If you only loosen the locknuts 1/8th to 1/4th turn, you will be very close when reinstalling the adjustors, as to swingarm spacing distance, and that will go a bit quicker.

11. It is at this point that you might want to add a support under the swing arm cross frame area, or under the exhaust pipes, whatever you decided to do BEFORE removing those swingarm adjustors! You might also want a bungee cord or two pulling backwards on the rear tire….perhaps to a ring fastened to your garage wall or from rear suspension to rear rack; or, whatever. A clever and CHEAP jack for the purpose of jacking slightly at the frame cross tube is in a photograph on the authors website: https://bmwmotorcycletech.info/hydraulicjack.htm
That jack has LOTS of uses.

Use a 6 mm Allen, remove the adjusters completely. Jiggle rear end to remove without damaging threads…or additionally pry a wee bit at the nuts…just do NOT bugger up the threads! The support will keep the rear end from moving much, and the bungee at the rear tire or suspension to rack/etc… will help pull the rear drive assembly slightly to the rear during the following work. On some twin-shock bikes, I have been able to use the bungees between the lower shock mounts and the luggage rack on the rear above the taillight, with no need for the garage wall ring.

12. You might NOT have to do these steps (I did not on the 1983 or 1984): Disconnect clutch cable at transmission lever. Remove the lever from the transmission.  But, again, I like to service that lever….and….inspect the throwout bearing!

13. Check to be sure that in no way the transmission, once loosened fully, can fall down, or injure the neutral switch. NOW…holding both sides of the transmission, slide it back enough to COMPLETELY expose the input shaft splines. Please be careful, watch any rearward interference with the clutch lever and ears and neutral switch. The lever MIGHT go up against the swing arm and be pushed a slight amount, without any problem. It will likely be helpful to pull the rear wheel rearward and then pull again on the transmission. Arranging a constant pull on the rear wheel is nice on some machines. Sometimes an assistant is helpful, but hardly necessary with the rear bungees.

You can now install the 1″ wood pieces (probably 3/4 to 1 inch thick) between the transmission and the engine to keep the transmission separated from the engine….you need enough separation to have the splines out of the clutch disc.   You might NOT need those wood pieces.   Whether or not you use the wood pieces, you WILL be using a rag to clean the transmission and engine mating surfaces, prior to reassembly.

*** DO NOT PRY AT THE TRANSMISSION-TO-ENGINE INTERFACE WITH METAL TOOLS!!! IF YOU BUGGER UP THE AREA WHERE THE TRANSMISSION AND ENGINE MATE, YOU WILL NOT OBTAIN A SQUARE MOUNTING UPON REASSEMBLY (VERY important)….YOU WOULD THEN HAVE TO USE A FILE AND even SANDPAPER, ETC. TO OBTAIN A SQUARE FIT. Keep a watch on the clutch lever and lever mounting posts…but they are usually not of any problem…just do not go overboard on your prying with the wood pieces!    Do NOT injure the two metal clutch lever bosses at the rear of the transmission!

14. If the spline and inner transmission front face area is a real mess of oily dirt, you can clean using small rag pieces, perhaps with a trace of solvent. I clean the splines themselves with an acid brush (I shorten the brush to make it stiffer) and a solvent. Rotate the transmission input shaft by putting transmission in gear and moving rear wheel, to allow thorough cleaning. I strongly suggest using a cut down ‘acid brush’ (1/3 to half the length of the bristles shortened is just the right stiffness). Extend the brush length with anything convenient, a rod or dowel. I simply use strong duct tape to hold the metal tube of the acid brush to a wooden dowel. Once the greater mess (if any) is cleaned, you can use the acid brush, dipped into any decent evaporating solvent. I have two of these brush/rod/dowel setups, one for cleaning, one for greasing, have had the same set for years.  Some use old toothbrushes, and they work fine, although some plastic toothbrushes are attacked by some solvents, such as MEK or Acetone.

NOTE: While spraying a solvent from a pressurized can on the input shaft splines IS OK, DO NOT spray into the disc splines!! Do not overdo it, and if you use a spray, allow time for the cooling effect to disappear before doing the actual greasing. I find the brush cleaning works well. I also like brushing FROM the transmission side of the splines, forward….helps keep crud out of the transmission input shaft seal….just don’t brush so vigorously that you sweep crud into the clutch disc.  You could stuff a tiny rag into the clutch splines area.

NOTE: Flushing the transmission and engine cavities area you are working with is unlikely to do more than get greasy solvent on the clutch, so don’t generally do that. Cleaning with a pieces of dampened, not dripping, kerosene’d rag is OK.
Stoddart solvent, kerosene, mineral spirits, paint thinner….all of these are GOOD and SAFE solvents.

NOTE: if you see that the input seal of the transmission is leaking oil, it MUST be replaced. Oil from a leaky transmission seal can travel forward along the splines and oil-up your clutch. You will have to remove the transmission completely from the bike to change that seal, which is NOT difficult and NO transmission disassembly is required. Usually removal at this point simply means you undo the rubber bellows boot at the right rear of the transmission, undo 4 flange bolts, and remove the transmission.
Early warning note:  The pre-1981 transmissions have the pushrod inserted from the front, later ones from the rear.  Be very careful.  Early transmissions have a piece of felt wrapped around a certain place on the pushrod, later pushrods go into a seal at the rear of the transmission. Insert that later rod, oiled, smoothly, rotating during installation, avoid damaging that seal, transmission must come apart to replace it!

15. Since you now have cleaned all the splines, you are ready to lubricate THEM. DO NOT EVER GREASE THE DISC SPLINES. ROTATE the transmission input shaft using the rear wheel, to allow 100%-around greasing. Greasing only the shaft splines keeps grease from working into the disc hub itself upon reassembly. Some greases are more difficult than others to get properly worked into the surfaces of the splines; work the grease in with your acid brush that is marked for greasing, not cleaning. Shorter than new bristles will make the brush stiffer and work better.

***Use a good grease, preferably containing some moly.  Starburags & Optimoly were once specified.  They are adequate, but not as good as more modern greases.  Honda 60 moly paste works OK.  GuardDog GD525 or even GD570 are excellently good.  SIG3000 with moly is maybe OK.  Most any moly grease will work reasonably well.   The Honda 77 moly grease works OK.

The main properties of the grease you are after are stick-to-it-ness-stay-in-placeness during the sliding motion, and moisture and corrosive resistance.   Moly is a very good substance for SLIDING splines, and in you Airhead, the clutch disc splines DO slide on the input splines.

Back to the grease job: DO NOT apply huge amounts, a light worked-in coating is best! Keep the grease out of the clutch hub. DO NOT grease the end of the transmission input spline flat forward surface ….that will just throw grease into the clutch later on. A small drop of grease on the pushrod tip is good.

More acceptable greases: Chevron Ultra Duty EP NLG1 or NLG2 (moly added); Würth SIG3000 (with added moly); Texaco Starplex-2 with Moly for SPLINES use; Mercury Marine outboard spline lube 92-816391R4 (Napa 18-9200) (moly added is better).
NOTE:  Guard Dog GD525 is preferred over GD570; until I have more testing experience. (Guard Dog is no longer available, so this is now moot).

I have also used for the 30%+- moly I add to greases, a ‘war-surplus’ moly MILG-21164B or D, etc. You can use any common moly grease as an additive, and even Staburags or Optimoly PL. The Staburags that BMW used to recommend at 100% (I DO NOT) was NBU30PTM, as 07-559-056-992. That is discontinued. I do not like ANY BMW grease for the splines. While BMW has discontinued Staburags and the old Optimoly, if you have some, you CAN use it for the moly component of your mixture.  Note:  There is good reason to believe that NICKEL type anti-seize compound may be excellent for the splines.  I don’t have enough testing information on this yet. The brand to get would be Never-Seez, Pure Nickel Special.  This stuff is superior for the exhaust nuts too….it is a premium ANTISEIZE.

16. Clean the FLAT CLUTCH END of the input shaft of any excess that might have gotten there. NO grease is needed NOR WANTED there! Add a slight dab of grease on the clutch rod tip, pure moly if you have it, otherwise, what you have. If the rod tip is not visible, push on it at the rear of the transmission.

NOTE and Caution: If you have the transmission totally out of the bike, you may be tempted to remove the push rod, I suggest that you do not. Early models had a split cylinder felt on the rod that is hidden, and a bit of fun to replace or reinstall.  The late models have a hard-to-replace seal at the rear cover of the transmission, that does the same sealing.  DO NOT REMOVE THE ROD. MIND THE DIRECTIONS I HAD EARLIER HERE.

17. Now is a good time to clean the starter motor rear bushing-shaft area with a Q-tip. THEN, lubricate this bushing with ONE drop of engine oil. Let sit 10 minutes, wipe off excess. DO NOT allow any oil to get into flywheel area ring gear and clutch!!…put a small piece of rag there first in case you are unsure of your ability to not get oil all over the place! The rear nose of the starter has a high amount of pressure on it when the starter is in use, and a drop of oil here on that bushing will extend the bushing life.  If you are terribly anal, use a non-detergent oil, approx SAE 20 or 30.

18. Remove those pieces of 3/4″ or 1″ wood, and clean the transmission-to-engine joining surfaces. They MUST be clean and unfouled; or, remember, the transmission will not mate dead squarely when reassembled. You had better NOT have been metal prying at this interface! After double checking mating surfaces, you may now remove bungees holding the rear wheel backwards and reassemble the transmission to the engine. WATCH what you are doing…you are not crushing that left side brown grounding wire or clutch cable? Watching the clutch ears?….ETC.  You might have to wiggle the transmission a bit…or even move the input shaft a few degrees (via the rear wheel, transmission in gear) to allow mating.   NO forcing is necessary.

NOW… evenly install the air cleaner right clamshell or lower box, as case may be, gooping the 13 mm bolt and washer, and install all transmission bolts/nuts, bringing the transmission into full contact with the engine, and TIGHTEN EVENLY. Tighten the transmission bolts/nuts to specs, 14-16.6 ftlbs on early models and 24 ftlbs on /7 and later models. Most mechanics just put a reasonable grunt onto the nuts and bolts. Be careful you have installed washers in the proper place, and that the aircleaner (especially the rectangular 1981+) fits to the transmission and engine squarely and properly.

If the starter cover is off, be sure you checked the battery positive cable nut on the starter solenoid; I have seen many of them get loose.  Do have the cable lug end oriented to not foul the cover, and that the cover fits OK at the aircleaner metal….or fix that now. If you have an early round-type breather valve, you could inspect it now, or consider removing it and installing the later reed type valve, which is quieter.  Some models require the starter motor out to fully inspect the breather valve. It generally is not needed to be inspected unless it is the earlier ROUND DISC type of breather valve.

If you were plugging the vapor system, or removing the fuel solenoid system, or updating a breather valve, etc….do it before replacing the starter cover.

19. CLEAN the swing arm bearings area and install swing arm adjustors which still have the nuts on them, rather lightly hand tightened with the 6 mm allen wrench, roughly equal balanced side to side; and you will be close if the 27 mm nuts were not unloosened unevently and too much. It may be a touch tricky to get the adjustors into place, you may have to jiggle the rear wheel a bit. DO NOT bugger-up the threads. IF your swing arm bearings are the sealed type and you can see that they are, I suggest you use a sharpened scribe or other tool and puncture the seal in a few places, for proper greasing later.

20. Balance the swing arm side to side, usual procedure using a selected size of drill shank or allen wrench as a thickness gauge at the inside of the frame area. When the swing arm is balanced, tighten ONE 27 mm locking nut moderately. Now, go to the OTHER side adjustor, and tighten it, via your 3/8″ drive allen wrench to 15 ftlbs. THEN LOOSEN IT maybe a half turn, then re-tighten until you have 7-1/2 ftlbs (this is 7.5, NOT 75!!). You must reach this 7-1/2 ftlbs as you are rotating CLOCKWISE. Now recheck the swing arm balance with the allen wrench as width gauge, or using a convenient size of drill shank. If not equal, you will have to loosen the first side 27 mm nut and try a different setting on that side adjuster…and repeat the procedure. When you are done, the final adjustment is the same 7-1/2 ftlbs approaching from the tightening direction. Both lock nuts are to be tightened to 72-75 footpounds.   The equality between sides is NOT overly critical.  DO NOT make a bad mistake:  DO NOT tighten the pins to 70+ footpounds…the maximum is 15 during the procedure.

21. Grease the swing arm bearings through the allen swing arm adjusters, using a rubber taper tip adapter on your grease gun. If your bike has sealed bearings, it is possible to also force grease into them via a sharp needle adapter, but if you puncture them, you can grease via the allen hole.  You can get rubber tip greasing items from chainsaw places, or any autoparts store.

I like to grease enough that the “cavity” between the swing arm and the adjustor boss area is 100% full, and I smooth it 360° with my finger. My feeling is that this extra grease adds protection against rain, etc.

NOTE: If your intention was to fully service the swing arm bearings area [btw, these are of the same tapered type and size like your wheel bearings, up through 1984 models], you will likely have to disconnect the shock absorbers and U-joint, so as to remove everything more rearward, for proper access. This also applies to removing the transmission completely for such as access to the engine crankshaft main seal, clutch, etc. All this is not a big deal, and some mechanics just pull the entire rear this way anyway for the spline greasing. See Author’s website on those U-joint flange bolts!!!…because you may want to change them, to eliminate the troublesome locking washers.

22. Reinstall everything else…and do NOT forget the airbox center bolt, sealing it with a bit of gasket goo on the threads [and both sides of the washer on the rectangular airbox models], to avoid upwards leaking!

23. Reinstall the throwout and clutch lever parts if you have taken those off.  Be very careful about that C clip if you have it.  I highly suggest you see the author’s clutch article for information on replacing the pin and clip with reliable components:  https://bmwmotorcycletech.info/clutch.htm. Check the clutch adjustment, take a long long look-see over the bike, be sure you replaced everything properly and did not have parts left over, and everything was tightened up.

ADDENDUM:

(1) I recommend you disassemble the clutch lever area at the rear of the transmission, and the throwout bearing parts, and clean and regrease at least every 2nd spline greasing. Use soft NON-moly grease at the bearings here, except at the point the clutch lever contacts the rod end, where a droplet of moly is beneficial. This easy job can be done when everything is reassembled, or before the spline grease job. The rubber accordion at the clutch lever at the rear of the transmission should be replaced if it is in bad condition. There are three basic versions of the throwout bearing. Be SURE to read my article on the problems with the flat needle roller version (they tend to fail if not serviced), and my information on the swelling of the piston in the bore as the transmission heats. On the Author’s website, of course!   https://bmwmotorcycletech.info/clutch.htm

(2) If your shaft splines (and/or clutch disc splines) are mostly worn away, they will usually look rather pointy, and your motorcycle may strand you someplace with bad noises and ‘no-go’. Properly lubricated regularly, the shafts last almost forever.   But, don’t get worried needlessly, as the input splines, even brand-new, are small, thin, and look a bit pointy-ish.

(3) If you are re-installing the transmission, from such as clutch work or a transmission overhaul, etc…..you already have the transmission output flange disconnected. Information on the 4 special bolts at that flange, and a tool for torquing them properly, etc., are in the tools article on the author’s website. Here is the URL for the tools:    https://bmwmotorcycletech.info/tools.htm

REFERENCE material: I advise reading this…as it has a different perspective and more detailed information you will want to know: https://bmwmotorcycletech.info/inputsplinesthrowout.htm

Revised by the Author, 02/20/2021
Snowbum, ABC #1843
https://bmwmotorcycletech.info/index.html