PDA

View Full Version : Easy compression test for chainsaw?


terrapro
08-15-2010, 05:59 PM
I heard somewhere that if you hold the saw by the cord and it drops easily on its own the compression is bad. Would this always be true?

I have an stihl 029 I recently accuired for cheap that I can't get to run properly. With the plug out and a finger over the hole you can feel good pressure but when I do the cord test it drops pretty easily.

I have had the carb apart half a dozen times to no avail, anyone have any ideas? Should I buy a new carb or dig into the motor deeper?

dutch1
08-15-2010, 06:06 PM
To be a little more conclusive, connect with someone who has a compression gauge. What you describe doesn't sound good.

Pull the muffler and take a look at the condition of the cylinder and piston.

topsites
08-16-2010, 08:52 AM
I think those tests are probably about as conclusive as checking tire pressure
by pushing your thumb against the sidewall, somebody with years of experience
might be able to tell you something doing things that way but I would get yourself
an inexpensive compression gauge.

jkilov
08-16-2010, 04:03 PM
To be a little more conclusive, connect with someone who has a compression gauge. What you describe doesn't sound good.

Pull the muffler and take a look at the condition of the cylinder and piston.

Ditto.

Another simple way is to dump a tad of 15W-40 oil in the cylinder and give it a pull, if it's harder to pull your engine is dead.

Honestly take it to a shop, they charge $15-$20 for a compression test and you know where you stand.

terrapro
08-16-2010, 05:57 PM
Took the muffler off on th e029 todat and the cylinder was smooth as a babies butt but the piston seemed grooved?

Had it running for alittle after I put the muffler back on but couldn't get it to idle right but it had a good rev to it.

dutch1
08-16-2010, 08:16 PM
If you have some metal transfer evidence on the piston you likely have the same thing in the cylinder. That most often happens on the exhaust side but is not limited to that. Get a compression test on it before you spend any serious amount of money on it.