78 r100/7 cylinder BASE gasket (shim)

[sinjun68]

So after Much research I have decided it time to replace leaky pushrod tube seals. Written down all my notes have the list of parts needed, thought I was good to go when as I looked at my cylinders again closely (still on bike) it is very obvious there are cylinder base gaskets on there! Parts fiche, articles, online tutorials, service manual, nor online videos show that my bike should have these? I did see in one tutorial that sometimes owners add them to lower compression, and if present need to be used again.
Arghhh. complications. now I have to pull the cylinders off in hopes to figure out what type (thickness, material) they are, and find a source for them since they are NOT listed for my bike in any fiche I can find.
I guess my question is if I find them should I still use the recommended sealant (drei bond 1209) with them or is it unnecessary?
I really do wish they were not present since I finally got my confidence up to do this project and now there has been a monkey-wrench thrown into the plan. Oh well.
Any thoughts?
-chris

[Kurt in S.A.]

Chris -

I just finished a total overhaul of the top end on my Sep 1977 build R100/7. Refurbed heads, new pushrod tube seals, and since my cylinders were out of spec, I opted for a Sienbenrock kit which included new cylinders and pistons. The kit is a 9.5:1 compression pistons, up from the stock 9.0:1 for the /7. I opted to install a 0.66mm shim (it's the shim used on the R60/6 bikes to lower compression) which Ted Porter said drops the compression to 8.8:1...pretty darn close. Bike runs amazing!

In stock configuration, there was no base gasket or o-ring. I would suspect yours is the same way.

Kurt in S.A.

[Roy Gavin]

Motorworks in England has the gaskets in their " Popular Modifications" section.

They will lower your CR a little, of course, and will complicate torquing the head down and pushrod seal depth, so a little thought is required before you use them.

[chasbmw]

These gaskets come in two thicknesses........