Boxerworks.com

Hi - new to the forum and new to working on airheads - all British up to now! I'm replacing the pushrod seals on my 1978 -R100 (built March 78), and have a couple of questions. The kit of gaskets sent by a knowledgeable airheads guy, contained the big O-rings for the cylinder bases, but with one cyl. removed...no O-ring in sight. I understand they were fitted to later models and my engine would use a sealant at the crankcase/cylinder joint. I see on a thread here that Drei bond or Yamabond, etc are recommended. I have a tube of ThreeBond 1104 ("Liquid Gasket, semi-drying"). It is a gray, semi-liquid goop. Wonder if this is suitable, or should I try to find the other stuff mentioned above?

The cylinder that I do have off wouldn't budge until I used the withdrawal tool shown in Haynes, to get it started. Guess that means it had a sealant on the base. The little O-rings on the upper studs were hard and brittle, as were the pushrod seals. No surprise after 34 years (but just 32k mi).

Another little surprise was when I pulled the cylinder far enough to get at the piston pin circlips - they were external (on a groove in the pin), but the BMW dealer parts people had given me internal clips which would fit in a groove in the piston. Sheesh.

I plan to reuse the external circlips - the first had plenty of "spring" strength when I removed it. Bad idea, or workable? Would appreciate any wisdom from y'all on tips regarding reassembly.

Thanks, all!

Gidday Bob, welcome.

Three bond is good.

Buy new clips!

I have an 81 with a base I ring and a quality sealant is critical of you prefer no leaks.

Not sure about sealant and pre 81 (gasket) models.

Rest easy though, there will be some good advice from others soon.

Thanks for the info. Just had a light bulb go on..."drei" is German for "three" so the stuff in my toolbox is apparently the recommended sealant.

There are different types of three bond.
It's worth getting the right stuff even if it means buying a new tube.

Not sure where the other guys are.........must be asleep.

Check that the pushrod seals are OEM , with a name and number on them - there are some some unbranded seals around and they are junk.

And go easy on the torque on the cylinder head studs - it is easy to strip the threads, particularly the ones with the oil hole.

It seems that 22/23 ft lbs will seal the head so any more is just upping the risk factor.