Likes to race old junk.
Join Date: Aug 2009
Location: Innisfail, Alberta and Baffin Island, Nunavut Territory, Canada
Motorcycle: Singles, Twins, a Triple, Four's, a Six and an Eight!
Re: Compression Test Help Results
As a general rule, you should see no more than 10 percent variation between the highest and lowest readings.
So if this is a street bike, you're still more or less, within an acceptable range. and should be able to sleep at night.
Keep records and compare again, the next time you're under the tank.
Did you crank the engine over an equal # of times, for each cylinder?
Was the engine warm?
Are the valve clearances within spec?
If it's still apart, and you want to play some more...while testing #4, if you were to crank several more times than you had with the other cylinders, and you noticed the pressure pumped up another @10psi, it would be an indication that the rings are worn in that hole.
Last edited by Beairsto Racing; 01-07-2019 at 08:13 PM.