Sthil 025 wont start without primer and wort run right

Harley hog · October 17, 2020, 04:36:39 PM

Hi I'm new the site I'm looking a sthil saw for a guy I'm been working on saws off and on but this one have me stumped. The only starts at first if u prime it, when it starts its boggy and blowing gas out the carburetor, dont seem like there much exhaust coming out of the muffler , no screen plug tried without muffler no difference,check compression 145 psi ,check impulse line good, intake boot good, check spark good, replace gas filter,check gas hose, gas vent, tryed another carburetor on it wouldn't start but I took it off my running ms230 could it be crank seals I wonder any help would be appreciated

ladylake · October 17, 2020, 05:22:46 PM

Blowing too much gas back through the carb is a sign the piston skirt is worn too much or maybe scored from dirt ingestion. I'd put in a new piston and rings and also replace the crank seals as they go out on high hour saws. Steve

Harley hog · October 17, 2020, 06:06:07 PM

If it skirt would it still have lots of compression. I looked at the piston on the in the exhaust hard to really tell what the cylinder is like.

Harley hog · October 17, 2020, 06:09:56 PM

So a worn skirt would cause this not starting and with good compression

ladylake · October 17, 2020, 06:15:23 PM

Yes it can have real good compression due to the rings sealing good above the exhaust port. If the piston skirt is worn it will blow back though the carb rather than pushing the mix up through the tranfer ports. I've had saws like that. Steve