express compression

hey can anyone tell me what the compression on my 78 expres should be.IT WAS 60 WHEN I TESTED.Ive been only geting up to 27 on flats and 29 down hill.Ive guted the pipe checked timing and points they where all good.and i am looking for the web site that has the shop manual on it ,was on it last nite but cant find it now. THANKS MIKE

Re: express compression

there's a couple express manuals HERE break>

compression at cranking speed, wide open throttle, should be around 120psi on any of these little engines.

If it's low, squirt some heavy motor oil around the piston's edge through the plug hole. If compression improves the rings may be leaking..

Aside from loss past the rings, look for possible leaks anywhere above the rings, like around the head gasket or past the decompression valve or spark plug hole ..

find out precisely why something is leaking (warped head, wrong decompression valve cable adjustment, missing sparkplug gasket, etc) before cranking down hard on bolts and stuff.. Normal tightness should stop any compression leak if the parts are there and are in good shape.

Re: express compression

Jonas Quimby /

Just to make things clearer, the Express doesnt use a decompression valve. Dont want you spending hours trying to find something it doesnt have.

But yes, something's not right. It should be between 120 and 140 for a used engine, 160 for a minty mint one.

How many miles are on the bike?

Re: express compression

FIrst thanks. Any way it has a waping 1, 145

« Go to Topics — end of thread

Want to post in this forum? We'd love to have you join the discussion, but first:

Login or Create Account