Airhead Tech Pages

Rear Engine Seal Replacement on a R90/6

(This procedure will work on most Rbikes..however, some of the procedure will be different depending on Model/Year, check you Haynes or Clymer manual for specifics related to your bike- ed.)

by Matt Parkhouse

I used to be able to R&R a gearbox, in a good shop in an hour. To do what I've described here, working in front of the house (on a warm day), I would budget 3-4 hours. I have done this task maybe 100 times over the last 20 years. I certainly would recommend using more than this description to under take this work. A Haynes/Clymer manual at the least, a friend who has done it is best.


Parts and Tools


Replacement of Seal and Reassembly









Parts to have on hand...

Rear main seal, oil pump
Oil pump cover and 4 bolts (upgraded since /6 series),
5 new flywheel bolts
4 driveshaft lockwashers
4 driveshaft bolts
6 clutch bolts
New driveshaft boot if the old one is cracked or leaking

Special tools...

Clutch compressing screws (you can use bolts and nuts-less handy but works OK, or get from Ed Korn)
Flywheel brake (make out of bar stock or get from Ed Korn)
Rear main seal installer: from Ed Korn
6mm allen drive on 3/8 socket, torque wrench
10mm-12 point box end wrench ( I like Snap-on's)
1 1/16" socket (turned or ground down on outside)
Micrometer or calipers
Slide hammer with hook attachment
Impact screwdriver with large phillips bit.


Replacing Seal and Reassembly

More specialized tools:

BMW swingarm grease
Fiitted grease gun or chain sawnose-wheel greaser,

We left the bike torn down to the rear crankshaft. I like to use spray carb cleaner to clean parts and the usually grungy clutch compartment. Not unusual to go through 2 or 3 cans on this sort of job.