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Transmission Input Spline Cleaning, Lubrication, And Hints

Revised by the Author, 08/22/2015

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 suddenly spline failure

When to do it: Depends on year model and conditions you ride in, but probably every 12000 to 35000 miles.

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 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 2x4.
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

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