1979 R65 Rear Main Seal and Clutch R&R

[Jean]

Ok guys and gals, I've done searches and read through the "Oh the Horror" and have not discovered what I need to know!
Soon, there will be a 79 R65 in my garge with a "bad" (bad-hair day?) clutch and a leaking RearMain seal.
I did this job on my 78 R100s in '09 and after some sage advice from the forum, it went OK. I have the long screws for removing the clutch, etc. and so......
The question is, IS THERE ANY SUBSTANTIAL DIFFERENCE in removing the tranny, clutch, and flywheel on the R65 from doing it on the R100s? The R100s had the shifter with "extra" linkage so I have that under control.

Research has found the clutch on the '79 is the "old" heavy flywheel type - that the change was made in 1980 so it SEEMS to be about the same.
Apparently the Flywheel bolts are 11mm so probably do not need changing, but what about the driveshaft?
Is there an O-ring on the flywheel? This is not apparent from the MAX parts-fisch picture.

A link to a specific instruction would be nice if such an instruction exists, but if not, I'll just re-use the R90 one I have with my notes.
PS. Rob, I registered/joined the R65 forum to try and discover this info. No luck.

[Kurt in S.A.]

I'm not aware of any major issues/differences with the R65 setup versus the other bigger models. I don't know about the flywheel o-ring, though. You're right...thru the 1980 models, all clutches should be the kind with the heavy flywheel...the "clutch carriers" didn't start until the 1981 models.

Kurt in S.A.

[wirewrkr]

All R65 bikes have an O-ring in the flywheel. It's the same as all other Flywheel O-rings, which started in mid 1975.
The "heavy" clutch on the 79-80 R65 is not the same as the heavy clutch on the other bikes. It is used only on the R65 for 2 years, in 9/80, ALL BMWs got the new style clutch regardless of engine size or bike model.
Those bolts for the pre load of the clutch are different than other models too. Your bike uses a 6mm clutch bolt instead of 8 mm.
The O-ring is clearly visible in Max's BMW fiche, don't forget to check the oil pump O-ring too.

[Rev Light]

Watch the torque settings in the Haines manual if you are using one, the bolts are small and the torque specified will just snap off the heads. I have not got the manual in front of but have done this job on my 79 R65 - and overtorqued the bolt by not being quite as clever as I like to think I am.

The other thing to watch out for is the felt seal in the clutch actuation rod. Oil can migrate up this rod from the transmission and make your clutch slip as well if you do not have a good seal. I did this job twice for some reason : )

Rev. Light

[Jean]

Rev Light...The problem IS: the Clutch IS slipping. Bike was purchased used in January of 2012 and ran OK for a while but then clutch started to slip. VERY low milage, only 17K. Not enough in my opinion.
So it very possible the felt is the real problem with the slipping. I also suspect the "rear seal leak" might be the neutral switch, but can't tell yet. Bike is still NOT at my house.
Thanks for the note about the clutch screws. I thought they were the same.
I have notes on torque for metric screws...I have noticed from edition to edition of both Haynes and Clymer that they are a bit casual about the difference in torque and whether or not the threads are into aluminum or steel.
Although on my R100s, the flywheel screws were 11mm, I changed them out anyhow as I did not know if the flywheel had ever been removed and who might have tightened them THAT time. Replacement is really cheap insurance. I torqued them to 80 ft-lbs, BTW.
Another thing. Just read my old notes. I did all this in 2006, not 2009 as I said earlier. Time flies when you're having fun!!

[Rev Light]

Unfortunately, you wont know for sure until you open her up. Look for spatter on the rear face of the assembly, pointing to the outside of the clutch. 17,000 miles is not alot for a rear main seal either - but it is old. The thing about the rear mains seal is that it is on the other side of the flywheel and would have to be leaking alot to get on the clutch, assuming it has not been lightened and is full of holes like mine.

[Jean]

It's been interesting.
Last night I got a call from the owner's dad who said he'd drive up to Clemson and trailer it "home" as he has a lift and didn't relish working on the floor.
So I may not know until next year at the Boone Rally what got found.
I'll call and tell him to have a look at what you all have written.
Many thanks. If another R65 comes my way, I'll have a good set of notes!!

[Deleted User 287]

Well Jean, this new job is really cutting into my forum-posting time.

I see you got all of the answers you need in time not to need them. But yes - the flywheel has the o-ring.

[Duane Ausherman]

It is all but impossible for a rear main seal leak to get oil on the clutch. You really only have two possibilities. One is that felt seal which is not likely, but possible. The likely one is the front seal on the input shaft of the transmission.

[Jean]

Agreed, Duane.
My rear main seal was leaking badly but the clutch was CLEAN. I replaced it because it was worn so much.
Speaking of "worn", my older manuals say the wear limit on the disk is 4.5 mm (mine was a bit over 3) but the latest Clymer manual I have (2003 edition) says the wear limit is 2.8 mm. Isn't THAT interesting?
I think if the disk starts at 6 mm and wears down to 2.8, you might not have much spring pressure left and you'd be slipping some.