compresion tester

[tannaj2]

I just bought a compression tester. my question is I was thinking it would be something like 120 psi of coarse that's not the case. according to the book my compression should be 7.7:1 high speed and 9.2:1 low speed. now its my understanding that the spark plug has to be removed to do these tests. so what in the world do those numbers mean and how do you know how to hit those numbers.

[s10gto]

You were on the right track ,but confusing Compression PSI with Compression Ratio. The Ratio affects the PSI. The cylinder ratio is how tight the piston is packing the air/fuel mix into the combustion chamber. For example if you had a engine with a 9to1 ratio you may see 120psi. If the engine had a high ratio like 12to1 you may see 170psi.

Screw the tester in the plug hole. Hold throttle full open. Kick bike until the needle stops rising.

Hope this helps.

[s10gto]

Also hold the kill button or ground the plug wire so you don't harm the ignition system.