Small Engines (Lawn Mowers, etc.): Gasoline in crankcase

Question
My 10 hp Briggs and Stratton riding mower has been sitting In my garage over winter. I pulled it out drained the oil to refill for this season.the gas that had been in the tank, had drained into the crank over the winter. What causes this,and is my mower ruined?

Answer
The problem you described is very common...gas leaked past the carburetor inlet needle seat.  The float could be bad, the inlet needle or seat could be bad, or there may have just been some debris or water in the fuel that caused the inlet needle to leak.

You should remove, dis-assemble and clean the carburetor with compress air from an air compressor.  Inspect all the aforementioned parts and replace as necessary.

Your other option is to just install an inline fuel shut-off valve and turn the gas off when you are done using the mower.  If the gas is turned off then it can not leak into the engine.  This is the cheapest and fastest option...you just have to remember to turn the valve off.

Make sure you use clean SAE-30 oil.  You may want to change and re-fill the oil a couple of times to remove all the gas that leaked into the engine oil.

Eric