On 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.
The bike was placed on the center stand. I disconnected the battery, and removed the seat, fuel tank and side covers. These I placed away from the work area where they would not be disturbed. Next I removed the battery and battery tray, which was incredibly difficult as there is very little room in the frame to accommodate them. The carbs, the air intake ducts, and the air cleaner assembly were all disconnected and removed after the fuel was drained from the carb bowls and fuel lines. The fuel crossover lines were also removed.
The mufflers came next. At this point, I decided to drain all of the motor oil (which was probably not necessary, but would have to be done anyway as the bike was due for an oil change,) and the drive shaft oil. I left the oil in the rear bevel drive (rear differential,) as the entire swing arm would be pulled out and the oil would not be disturbed unless it was tipped forward. (I made sure to place the swing arm and rear drive on a level support after I removed it.)
Following the directions of the manual, I removed the forward clamp and peeled back the drive shaft rubber gaiter. I could now see the four bolts which connected the drive shaft to the gearbox. I tried using my six-sided 10mm box-end wrench and found that it would not fit on the 10 mm, 12-sided stretch bolts. I jumped on my Vespa and rode to Sears. After searching through the various wrenches and consulting with one of the employees, I had the correct wrench. The bolts were tight, but by using the rear brake to prevent the drive shaft from turning, I was able to remove the bolts and put them aside. BMW insists that these bolts cannot be reused, and since they only cost a couple of bucks, there is no need to.
I placed a piece of two-by-six lumber underneath the center stand and removed the rear wheel and tire. I also removed the rear brake pedal, brake rod, and right foot pedal (which I also found to be unnecessary.) Before removing the lower bolts on the shocks, I placed two boxes underneath the swing arm to support it's weight. With the shocks and the rear rack out of the way, I was able to remove the swing arm. Using a flat head screwdriver, I removed the dust covers and exposed the swing arm adjusting bolts and locking nuts. I noticed the locking nuts were larger than any socket I had in my tool box, so I called a BMW mechanic who said the socket I would need was 27mm. He also mentioned that the socket would have to be machined in order to fit into the frame tube. I rode back to Sears to buy the socket. Unfortunately, I only have 3/8" and 1/4" drive ratchets. The 27mm socket only came in 1/2" drive. I bought the socket anyway and as an afterthought I bought a 3/8" drive swivel-head breaker bar that I had been eyeing for some time. I knew it would come in handy. On the way home, I raided my fathers tool box and found a 1/2" ratchet. I got the locknut off and removed the Allen head bolts, which freed the swing arm. I placed it on a Volkswagen spare tire, and this held it perfectly horizontal and prevented the rear drive oil from leaking.
I now had access to the gearbox. Although not necessary, I drained the gearbox oil and removed the left foot pedal and the gear change mechanism. I disconnected the clutch cable after slackening the adjustment bolt, and removed the circlip, pin, spring, and clutch operating lever. I noticed that there were a total of four bolts connecting the gear box to the engine, three of which were Allen head and one of which was protruding from the case and had a 12mm nut on it. I found that my Allen wrench set would not fit on one of the bolts, so I had to go to the store a third time in order to get a 6mm Allen wrench-specifically, one that was "L" shaped. About eight hours after I began, I finally succeeded in removing the gearbox from the bike. I was exhausted and quit for the day.