Small Engines (Lawn Mowers, etc.): Problems with a 5 hp craftsmen lawnmower motor, new spark, plug hole

Question
I have a 5hp craftsmen mower model #917.387230 that has been sitting for 2-3 years unused in the back yard. I went ahead and put a new spark plug in as the old one was corroded heavily and primered the gas. When I tried to fire it up, gas was blowing through the exhaust and oil would squirt out a rubber overflow valve of some sort. The engine comes close to turning over but it just doesn't happen. I'm about to start disecting the motor to see what needs replacing so if you might have any advice to offer me it would be greatly appreciated.

Thanks,
Brandon

Answer
Hi Brandon,

Drain and re-fill the tank with fresh fuel if you haven't already.  Check the oil level to be sure it is not over full.  The valves may be sticking, so add a couple of tablespooons of oil to the spark plug hole and slowly pull the engine over several times to coat the moving parts.  Try starting again.  If still not good, check the compression.

Let me know how you make out.
Michael