1979 R65 - cylinder base gaskets - or not?

[steve hawkins]

We have the top ends apart on Tony's bike, it looks like the pushrod tubes were never leaking.  It actually looks like the oil leak was coming from the interface between the cylinders and the crank case.  The oil seems to have been getting passed the rubber 'o' rings.

We did notice that there was no cylinder base gaskets either.  Assuming that there was none when I first did the bike, so why the leak?  It was 11 years ago the cylinders were last off.

Have I missed something?  I did not used any sealing compound on the interface though - it looks clean as a whistle.  But the oil is definitely getting passed those rings.  Was anything retro fitted?

Photo's to be added when Tony gets his sh*t together....

Rev. Light

[Bob_Roller]

There's nothing more than an o-ring to seal cylinder base, no base gasket like earlier bikes had .

Upon reinstallation, the o-rings need to lubricated, engine oil, or some sort of grease, just so you don't roll the o-ring when you put it back together again .

[Dustybin]

Thanks for the quick response, photos are on the restoration blog

[georgesgiralt]

Hi !
I changed the rings on my '82 last November.
The bike leaked at the cylinder base. Lightly on right side, more on left side.
I did oil the O-ring and did not use sealant on the interface.
So I decided to stop the leak last October and put new O-ring and, this time, put Permabond liquid sealant at the interface between base and cylinder. No leak so far. The O-ring I removed had no problem. Supple and not torn.
I suspect that something is a bit warped due to age (these parts are more than 30 years old) because when I first changed the rings, a long time ago, I did not put sealant nor gasket and had no leak then. Or maybe the O-ring are not what they used to be ?
So now, it is Permabond and basta !

[Barry]

O rings cylinders ought not to need sealant but Permabond is so often recommended as a matter of course that the O rings must be fractionally undersize in section. Either that or the grooves are too deep.

[nhmaf]

As the others have mentioned - the o-ring cylinder bases on the R65 / R45 do not use a base gasket, and while they *may* not technically need a sealant applied to the cylinder/case interface, EVERYONE I know does do it and it ensure an oil tight seal when done properly.   You want to use a VERY THIN, even coating - just enough to tell that it is there - and mind that you keep it away from the upper studs where the oil galley trickles engine oil out to lubricate the rocker arms.

Permatex and Yamaha (YamaBond) make suitable products for this application, as the originally specified Hylomar is increasingly difficult to obtain, and some claim it isn't as good.   I've got the Permatex and Yamaha stuff myself.   These can also be used to help the push rod tube seals stick/seal well against the engine case too.   Again, the key is to use a thin even coating.

[montmil]

...  Again, the key is to use a thin even coating.

Really, r-e-a-l-l-y thin. THIN.

[Dustybin]

thanks gents I will use a very thin coating when I put it all back together and I will lube the seals. Got my bag of new gaskets and my new drive shaft couplings in the post today! So i am going to be busy