Chainsaw Compression Testing

olyman · Jun 14, 2021

grizz55chev said:
Check the dates on this thread

so what?????????!!!!!!!!!!

dave84smith · Aug 5, 2023

Wood Doctor said:
Look for 150 PSI

That's about the average. Anywhere from 140 to 150 is pretty good. The saw will probably run if compression is as low as 90 to 100 psi, but reports have varied on this issue because of timing. Spark timing is very important--probably more important than compression. If the timing is off, the compression is almost meaningless.

Hey wood doctor, I just finished rebuilding the top end on my Husqvarna 61, I did a compression test on it before running it the first time and it came in at 145psi, I have since put some fuel into it and let it idle to break it in. It now reads between 130 and 135psi, is it normal for a saw to drop in psi like that and is that okay sitting at that amount? My tester is a newer gauge, I don't think it's the issue.

dave84smith · Aug 5, 2023

dave84smith said:
Hey wood doctor, I just finished rebuilding the top end on my Husqvarna 61, I did a compression test on it before running it the first time and it came in at 145psi, I have since put some fuel into it and let it idle to break it in. It now reads between 130 and 135psi, is it normal for a saw to drop in psi like that and is that okay sitting at that amount? My tester is a newer gauge, I don't think it's the issue.

Sorry I made a mistake, it started at 140 psi and is now between 130-135

cookies · Aug 5, 2023

dave84smith said:
Sorry I made a mistake, it started at 140 psi and is now between 130-135

Go run it hard for a few hours or all day... remember to idle a minute or two before shut down to help cool. Retest after, this seats the rings to the cylinder walls.

dave84smith · Aug 5, 2023

cookies said:
Go run it hard for a few hours or all day... remember to idle a minute or two before shut down to help cool. Retest after, this seats the rings to the cylinder walls.

@cookies I'll have to hit some wood with it, is it a bad indication though if it were to drop like that?? I can still feel the compression when pulling over, it doesn't pull over easy like it did when it had the bad piston in it.

cookies · Aug 5, 2023

I wouldn't worry about it unless it suddenly has hard starting issues or failure to maintain rpm at idle

stihltech · Aug 6, 2023

Compression guages are just a cause for concern that is not even recommended for 2 stroke equipment. Visual condition and leakage tests are MUCH more important. As said before if it performs well RUN IT!