Small Engines (Lawn Mowers, etc.): tecumseh stalling problem, lawnmower engine, head bolts

Question
HI John,

l got an 2 year old tecumseh lawnmower 148cc. its starts but dies after about 30 seconds of running or so.it will restart then dies shortly afterward, it surges a little when its running. now l've checked compression and its low reading anywhere from 50-60 psi. l checked the head bolts and some where loose around the valves, so l proceeded to remove the head and check the gasket it was ok, but the cylinder wall was in very rough shape scored badly hence the low compression, and the intake valve had a fair amount of side to side play.

MY QUESTION: #1 what is the miniuim amount of compression  needed on a lawnmower engine to run properly (approx). #2 can low compression cause stalling and hard starting in the case with this mower or any other.

Thanks in advance

Doug

Answer
From what I've read the compression should be somewhere around 80 psi., when warm. Your engine, like most small engines, probably had a compression release which makes it hard to get an accurate reading,but if you have scoring in the cylinder it may be too late for testing. If your engine runs for a little bit then dies and won't start but for a few seconds it probably is worn out and losing compression. Proper compression is essential for your engine to run.