Nikasil

[richard t]

How can you put a base gasket (or o-ring) under the cylinder without removing the cylinder?

First, you place the pistons at top dead center. Then you pull off the cylinders just far enough so you can get access to the clips that hold the wrist pins in place. Once the clips are removed, you can push out the wrist pins and continue pulling the cylinder with the piston inside. Be careful that the connecting rod doesn't drop and slam against the engine opening edge.

I'm not sure how easy all this is to do. In my limited experience, access to the clips can be difficult and you will need special pliers to extract them. On the /2 models, the clips are actually stiff split rings which fit into a groove which are very difficult to get out. The clips on my /7 were external to the wrist pins so were somewhat easier to get to. On the Siebenrock kit I installed to replace the entire top end on my /7, the clips are now like the /2 models. IIRC the wrist pins are slight interference fit. In order to get them out, you need to use a hair dryer or something to heat up the bosses that hold them.

You're doing all this while holding the cylinder in the air with your 3rd hand. I'm not sure the hassle is worth it. Not to mention you have to repeat the process on installation.

Kurt

It's not all that hard to do. as Kurt said "be sure to pad the eng case or third hand to keep the rod from hitting it, also have extra clips on hand or you will lose one. I use a wooden dowel rod tp push the wrist pin out. I did the 1974/6 that way because it has never used any oil and I didn't want to chance braking a ring

[Zombie Master]

So pulling off the piston can create a problem, if you use the original rings?

[Wayne J in MA]

I have pulled cylinders w/heads off a dozen or so airheads over the years with the pistons with rings staying attached to the connecting rods.
I just use Duane's finger method to insert back into the bottom of the cylinder. I have never broken a ring or had an oil usage issue after this work. Just be slow and gentle putting the rings back in. It helps to have someone assist in holding the cylinder although I have done it alone many times supporting the weight on my upper legs.

[Zombie Master]

Did you worry about the ring end gaps position?

[Wayne J in MA]

According to Duane they move over time anyways but I just left them in the position they were in coming out. I don't recall even looking except maybe the first time.
You need tough finger tips with this method. Guitar playing probably makes yours tough enough. Easy to pinch finger tips though.

[Wobbly]

Why not replace the all the sealing pieces without removing the pistons? Assuming before you take it apart and check compression.

If you had just put new rings in the bike, then that might be OK, but you really need to measure the ring end gaps before reassembly. A compression test will tell you if the compression rings are working, but nothing about the oil control ring. The only way to know all about both functions is to pull the piston.

[Wayne J in MA]

I agree. In all my cases I had good compression and oil consumption. I was in there to fix oil leaks, base gasket or push rod tube seals.

[ME 109]

ZM's bike hasn't had a hard time or too many miles, iirc.
Assuming this is just to fix an oil weep at the cylinder base? Or is it a matter of fix it as well, while doing the pr rubbers?
I pull the cylinder with the head, piston inside. My wrist pins are easy to get out, and just require basic circlip pliers to remove clip. Zm's should be the same. No heat required.
Worry more about a suitable sealant, less about the oring. I have very good results with Three Bond.

[Rob]

Worry more about a suitable sealant, less about the oring. I have very good results with Three Bond.

Wasn't Yamabond the hot ticket, for a while?

[Zombie Master]

Worry more about a suitable sealant, less about the oring. I have very good results with Three Bond.

Wasn't Yamabond the hot ticket, for a while?

Yamabond was great stuff. But who knows these days.