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


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?

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 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.


Small Engines (Lawn Mowers, etc.)

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Eric A. Jones


Lawnmower Repair . Certified Master Service Technician from B&S. Have 23 years experience on B&S, Lawn Chief, Weed Eater, Echo, Peerless, Wheel Horse, Snapper, Atlas, MTD, McCulloch, Homelite and many other numerous brands. Specialize in electrical repair.


Born and raised in the midwest. Started tinkering with engines when I was about 14 on my Suzuki RM-80. I began lawn mower repair at a small hardware store. I knew absolutely nothing. I read lots of repair manuals and met an older fellow who taught me many lessons. I continued working on small engines through high school and paid my way through college working on mowers at the same hardware store. Decided to get away from the midwest and mower repair so I joined the Air Force. I repaired air traffic control electronic equipment and ended up in Hawaii where I got a part time job at Small Engine Clinic. I gained a lot of experience from the Small Engine Clinic and had a blast repairing small engines. I then took the Briggs and Stratton Master Service Technician test and earned my MST. I then traveled to Wisconsin where I attended the factory update training seminar and received formal training. Continued working on mowers part time as I completed 20 years of military. Retired from the military on a Friday and continued in the lawn and garden industry the next Monday.

MAS Aerospace Operations BA Mathematics AAS Electronic Communications AAS Electronic Technology

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