Ok fellas I have pulled my old R75/5 all apart for more reasons than just one but this is on the list to repair. I have had a small leak and assumed it was the rear main. After pulling things apart I really dont know if the main was leaking at alll. I will replace it but it looks to me as if this lower plate may be the actual culprit, what do you think? I know it's hard to see but the main seal looks in tact. Could it be the lower plate seal also?
From your pictures, I would say you're right, it's the oil pump cover. There's an o-ring under that cover. If it were the rear main, I'd expect to see oil thrown all around, not just down.
It looks like that is the original rear main seal. Make sure you change it. It has served well but it's time to go has come. The oil pump cover O-rings do go bad and leak.
I think I will change the rear main as well as the oil pump plate seal; hopefully that will do the trick. As far as blocking the crank I am unfortunately in the dark, what do you mean?...please advise.
STOP! If your crank rotates it may shift forward coming off the thrust bearing. http://bmwmotorcycletech.info/flywheelremovalwarning.htm
OK call me stupid, I'm sure the thing rotated at least 90 degrees but I marked it and put it back where it was when I started. How does it come off the thrust bearing? I don't understand...isn't the thrust incorporated into the mains?
Some good detective work there jackd. Those dowels/pins that retain the thrust washer are about three mm long from memory.
That oil could not only be from the tranny input seal but it could also be from the clutch rod. You need to look at ALL the possibilities. It might be from the RMS too. I can't tell from those pictures. If that isn't the original seal it is the original type. The later types are SO much better. I would replace it. I would be tempted to replace that original oil pump cover for the same reasons. Plus it very well could be a big source of the oil.
My later type oil pump cover sent me on a freakin' wild goose chase when it developed a hairline crack in the top left counter-bored hole. It presented symptoms of a leaking rms or worn guide ring or guide ring o-ring. I was advised (by GSPD) to run the motor without the tranny and clutch installed. Bingo! the leak identified itself almost immediately. The earlier angled counter-sunk type covers could not present this issue imo. I am proud to be the recipient of never before heard of airhead problems. True pioneering
Make sure you chase out the bolt holes for the oil pump cover. Previous owners/mechanics may have used Locktite to hold the bolts. Since the torque is only about 7lbs, any interference means the cover isn't seated..and will leak...again. Actually, I think you should use some blue so the bolts stay in place.
I always heat them up in case some numnut has put red loctite on them. I always chase those threads. Not with a cutting tap but with a thread cleaner or a roll tap.
Ah, the joys of having the same motorcycle for coming up twenty years. I know exactly what the numbnut has done.
Not so sure about that. I would think that an over torqued countersunk screw could cause a crack easier than a flat bolt head. I realize that I'm comparing apples to oranges ( plastic vs. steel ) but I saw so many leaking neutral switch plates on RDs due to cracks from over torqued C/S screws. The key was loctite and just snug the screw enough to seat the cover and compress the O-ring. Let the loctite take care of the bolt retention.
The counterbore for the bolt head is what caused the problem. The bottom of the counterbore is ever so close to the o-ring groove on the other side. Perhaps my cover was somehow over machined bringing it too close to the o-ring groove. Mind you, this cover was at least 25 years old and had only been taken off once. Possibly over torqued.
