390xp compression

[Gavinmalloy18]

I have a very lightly used 390xp maybe about 5 years old. I checked the compression just for curiosity and it was only like 135. It runs great and starts great and has plenty of power. I tried two different testers. Any ideas? I bought it new.

 

[Gavinmalloy18]

It’s probably not even broke in yet, just curious if that seems normal?

 

[huskihl]

140-150 is probably normal. Might not be broken in yet

 

[Redfin]

What is your elevation?

 

[Gavinmalloy18]

I think around 1600’

 

[Ketchup]

If it runs well I wouldn’t worry about it. Compression testers usually aren’t very accurate.

But if you think it’s a problem take the muffler off and check out the piston. Roll the piston over and check the back wall of the cylinder too. If you see obvious gray scuffs or streaks then you might have a problem. Cuts or gouges are obviously bad. Light streaks on the back wall are usually just mix oil.

 

[Redfin]

I think around 1600’

Iirc the 585 was 135ish and Im at 2100’. I would not worry about your static as long as it runs good.

 

[Gavinmalloy18]

Okay thanks.