main seal – Airheads Beemer Club

Replacing Rear Main Seal – 3 (Parkhouse)

This will be a long one… So I’ll break the reply into two parts: Tear down and reassembly.

Parts to have on hand… Rear main seal, oil pump O-ring, oil pump cover and 4 bolts (upgraded since /6 series), 5 new flywheel bolts, 4 driveshaft lockwashers, 4 driveshaft bolts, 6 clutch bolts, a 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 [see Links]), a 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), 27mm or 1 1/16″ socket (turned or ground down on outside), micrometer or calipers, slide hammer with hook attachment, impact screwdriver with large phillips bit.

Place bike on center stand (if a “Ride-off stand”, block up on 2X4s), you want to be able to turn rear wheel freely. Drain gearbox if work is planned on it. Drain driveshaft as oil will spill when it is disconnected. Remove gas tank, set aside out of way. Take carbs off cylinders and hang over front of cylinders, out of way.

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Replacing Rear Main Seal – 2 (Floyd)

>>Oh, no! I noticed oil running (drooling?) out behind the trans. If my diagnosis is correct, what seal is it?

I presume that when you say “behind” the trans, you mean at the trans-case interface? If you mean literally “behind” it, as in out from the boot at the trans output, you can stop reading. If not, you more than likely have a rear main seal failure. That’s the seal where the crankshaft emerges from the case to marry the flywheel.

Tools?
Pitfalls to avoid?
Tips?
Other items to replace or rehab at the same time?

With the bike now up on an elevated table (we call it the “surgery table”) and with the final drive, etal all the way off, it would be a shame to take it to the dealer. Plus the $$$$$ consideration.

Then this is the IDEAL time to do it. You have to pull off the final drive to pull the trans anyway, and that is a big part of the labor. You will need a few special tools… a flywheel holder (holds it in place so you can unbolt and later bolt the flywheel to the crank), a set of three ( I think) longish metric *fine* bolts for backing off the clutch’s diaphragm spring, and finally a tool for seating the new seal to the correct depth.

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Replacing Rear Main Seal – 1 (Garcia)

n Wednesday I decided to start a project I have put off for months. My 1978 BMW R80/7 had been leaking oil, and I suspected the rear main seal to be the cause. At first the leak was barely noticeable, but grew worse as the months progressed. I called several different shops to find out how much it would cost to replace the seal, and was quoted on average three-hundred and fifty dollars. I had worked as an apprentice mechanic at a motorcycle repair shop in Santa Barbara, CA., under the expert tutelage of master mechanic John Ireland, but I had never tackled anything so extensive on my own. I realized, though, that if I did not deal with the oil leak soon, the clutch could be ruined.

I did not want to pay for a new clutch as well as a new oil seal, so with tremendous amounts of anxiety and trepidation, I began the project by reading about the procedure in my Haynes workshop manual. I concentrated on the parts that did I did not understand, and attempted to visualize the sequence from beginning to end. Next I cleaned the garage and made sure all of my tools were in proper order. I found lots of newspaper, rags, and some cardboard boxes for parts storage. All of this preparation was crucial, since I had recently moved, and was not used to my new garage.

I missed the workshop I had built at my old house, where I had the luxury of space and light. Now I was in a cramped garage with poor lighting, so I would have to adapt. I discovered that I would have to disassemble many of the major components of the bike, as well as buy or fabricate some of the special tools that would be necessary for the job. This seemed daunting, especially since I do not have a compressor, a grinder, or a bench on which to work on the bike. Nonetheless, I started with the basics. I knew that if I kept focused, patient, and creative, the job could be successful.

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