compression 400ex

[QuadRacer18]

how much compression should a 400ex have when doing a compression test to see if it needs new rings? thanks, josh

p.s. if you put your thumb over the spark plug hole and turn it over and it pushes your finger off the hole this will show you have enough compression right?

[1fst400]

I would say anything over 80psi would be good. no holding your thumb over the hole isnt an accurate test.

[GPracer2500]

Service manual says normal compression is 100psi-128psi.

[-copyguy-]

QuadRacer18, sent you a PM that might be useful...