Another Cautionary Tale

I did a compression test on my new E-Bay 850 non-runner with my year-old Sears thread-in unit, which replaced one from the Seventies. I got 31 psi on one side, 32 psi on the other with the throttle wide open, half a dozen kicks each side. Valve gear had plausible slack at TDC all around.

I then spent an hour pulling the head, finding fasteners torqued to spec, a tightly sealed head gasket, valves in superb condition and 40-over pistons sucking smoothly through bores with practically brand-new cross-hatching, crowns and milled head dusted with the carbon patina of a perfectly adjusted four-stroke.

A test on my strong-running 50 mpg '72 Combat produced 31 psi on each side, proving yet again there is no fool like an old fool. Has anyone put Sears' return policy to the test recently?


Tim Kraakevik
kraakevik@voyager.net

Tim,
Around 135 to 150 PSI is what a good working 850 should produce. I don't understand why you pulled the head? A gauge reading of 32 PSI is double ambient air pressure, there would literally be no compression felt in the motor all. If you stuck your finger in the plug hole and pushed down the kick start that would tell you if there was compression. A gauge will specifiy what it actually is, except yours is probabaly defective. Can you elaborate on the symptoms?

Mick

I'm loosing my faith in Craftsmen products. Definitely not half as good as they used to be.

Hey Tim,
31 and 32? that's only 3% deveation. Not bad.
I was idling in the driveway last Friday warming up to go get an inner tube for wifey's 650 funduro when it just quit. Thank god I wasn't running. 0 compression. Valves weren't moving. The cam chain lost it's master link. The semi local British bike mechanic had a chain, gasket, and pump washer. All's well.....but Man o man. Back to 150/150.

pvisseriii said:

...The cam chain lost it's master link...

Click to expand...

YIKES!

Lucky you avoided bent valves.