MS310 Compression

[Automender]

Just helping out a friend checking compression on his MS310. I heard it bogging down while cutting a 16 inch maple log with a brand new chain the other day. We got 120 psi on my tester that has a valve at the adapter that screws in the jug. Not sure what the factory compression value is? Any idea of a reasonable compression for a well used saw should be?

 

[Backstage]

120 is a touch low, but not out of bounds for a 60cc saw. I have a 55cc saw that pulls in the 130s with a perfect piston and cylinder. If you’re worried, pull the muffler and look for scoring.

 

[cscltd]

Fuel lines are weak points on the ms310 family that suck in air as it comes out tank. Buy original Stihl one

 

[mountainlake]

Keep in mind any saw will bog down if you lean on it too hard with a sharp chain. 120# is low if your gauge is right, should be around 145# +. Pull the muff and look. Steve

 

[Automender]

Thanks for the replies. I was thinking since it didn't have a decompression valve that the compression would be lower from the factory. It actually was 125 not 120 psi plus my gauge is hard to tighten in the cramped sparkplug holes. I need to solder on a extended handle or something to help tighten it.

 

[stihltech]

Does it stay up if held by the starter handle? Ditto on the fuel and pulse lines. Pull the muffler and check piston condition.

 

[Chevboy0167]

Times 3 on the fuel and impulse. Especially the impulse as it makes 2 S-shape bends that tend to crack and form holes, sucking in too much unmetered air causing a lean fuel to air mix. This is when scoring pays a visit to the top end!