Valve guide seals and oil incompatibility

[Mr Bump]

Just a thought really...

I'm doing a top end refresh on an xr400 for a friend of mine, the engine is in good condition apart from the valve guide seals which seem to have abruptly failed all at once and quite badly. The seals are quite soft, not hard and brittle like they often are when they fail.

Another friend of mine is having a fairly torrid time rebuilding a klr 650. This bike uses the same valve guide seals and guides as z series motors. He built it first off using genuine valve guide seals, which appear to have leaked quite badly straight away. They were fitted properly apparently, he's now rebuilding again with new guides too as he found one guide was worn on re-inspection. Don't explain why both exhaust seals (at least) were leaking.

By contrast, I rebuilt my z1000 a couple of years ago, cutting a long story short I used the cheap guide seals out of a vesrah (I think) kit and its given no issues at all. I run it on motul 5100 oil.

I'm wondering if some oils aren't compatible with certain seal materials and are causing them to give up prematurely, maybe swelling up?

Olly

[Mick J]

It's a long time since I did it, but I rebuilt a Klr 650 Tengai engine and from memory, the valves are inserted into the head and sellotape or similar tape wrapped around the top of the valve stem, then oiled and the valve guide oil seal slid down to avoid damaging the seal on the collet groove. I don't remember having a problem. Sorry if you already know this, but if you don't, it might help. I don't know about the oil compatibility.

[warren3200gt]