Just bought a used Murray 40508x92a. It has been sitting for 2 yrs, garage kept. Its a 12.5hp Briggs and Stratton engine. When I got it started it smoked a little and then cleared up and ran fine. I bought the mower and then 3 days later I went to use it. It smoked badly and wouldn't stay running. When I checked the oil it was extremly thin and I believe it is full of gas. Where should I start looking for problems? What is the most likely problems? Is the motor ruined?

Wtstoney, March 2011

carburator needs new needle and possable a new float

clarys small engine clary, April 2011

This is a classic symptom of a leaking carburettor float needle valve. Strip & clean the carb - chances are that's all it needs. After you woke it up - and disturbed whatever crud may have been in there after 2 years of storage - something has lodged in the valve seat. While it was running, it was fine, but when you parked it for a while, the leaky valve will let fuel run into the engine where it will dilute the oil. Just change the oil - as long as you didn't run it that way for too long, the engine will be fine. You'll know immediately - because it will either be OK or it will sound like a bag of bolts in a cement mixer.

phil_saunders(a)bigfoot.com

Phil Saunders, March 2011