Compression Question

1.What should my 1979 KZ650 SR compression be?

2.#1 cylinder is cold to touch while running.

Bio on bike= been sitting for years, carbs have been rebuild, new points and new spark plugs, static timing has been done. coils have correct readings.

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Compression issues should be in the engine section. I am moving this thread. wiredgeorge/moderator

Post edited by: wiredgeorge, at: 2006/02/09 08:36

I think it should be any where from 120 to 150 psi, depending on engine wear. The cheap handheld testers are not that accurate. Is that the exhaust pipe on #1 that is cold. That would not be good.

150 PSI sounds good, measured with the bike warm, and be sure to hold the throttle WIDE OPEN while testing. The choke should be open also (lever pushed all the way down).

If you've got over 100 compression in #1 and fuel and air and plug boot is good, it's got to be your plug. Buds XS650 quit firing on left last week and it was the plug. Looked good, made spark when out of cylinder, but wouldn't fire on either side when installed.

-Duck

I've heard that some bad plugs can fire in the open air, but when subjected to the engines compression they don't do a thing.