Take the cylinder barrel off the engine and do an inspection on piston and barrel, had a similar problem but the bore looked ok so changed the piston for one I got on ebay with two piston rings (std is one ring), I now get 140psi and the saw drops slowly when suspended of the rope starter. I expect the compression to improve with use - I get 170psi on my 345!
Steve
February 2009
Slightly scored the bore and piston resulting in a partial loss of compression. Won't get any better and will only get worse. If you repair in NOW you may get away with just a new piston and rings. Later on it's going to be a new barrel as well.
pleasant
February 2009
Automatic Answer
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