stihl 011 avt problem

[dolmarphil]

hi, i have a stihl 011avt in repair and i dont find the troubl.to keep the saw running,i have the L screw open about 2 1/2 turns out.i replace the fuel filter,fuel line,vent hose,spark plug and the carburetor gasket.I do a pressure test and it there is no leak anywhere.


But i take the compression on the saw and cold it give about 130 Psi and when warm it drop to 90 Psi.The piston look good with no scratches.Could it be the piston rings that give me this trouble?

 

[blsnelling]

Wow. I'm not sure what to tell you. If you're that far out on L, you're getting excess air from some where. I'm surprised the saw even runs if compression is that low. Is there a Schrader valve in the tip of your gauge?

 

[dolmarphil]

yes there is a scraeder valve on my compression tester,but i think is on the way out because i opened the saw and chck the ring ,piston and cylinder and all was fine.

now i suspect a leak but where?i pressure test the saw and everything was ok.the only thing that i can see is that the carburetor gasket as a small leak

 

[bama]

Would a vacuum leak cause this? I thought I read that saws can show good on one and bad on the other. Don't know if this is the case, but does it hold vacuum?

 

[dolmarphil]

i dont test the vacuum,i think i will do this first before checking anything else

 

[bama]

i dont test the vacuum,i think i will do this first before checking anything else

It may not be the cause, but I am curious if that is where you are leaking.

 

[dolmarphil]

ok,check the vacuum,let the saw sit with the vacuum for10 minutes,no leaks at all.

I'm gonna check the carb gasket,think this is the only thing left that can be faulty.

 

[blsnelling]

A carb gasket would do it. It's letting in un-metered air.