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Small Engines (Lawn Mowers, etc.)/14 hp I/C Briggs & Stratton eng making oil


This engine is on a Craftsman rider mower and I have been having starting problems. I normally always checkthe oil but becuase of starting problems I have not done so lately. Today I decided to troubleshoot the starting problem and as battery was charging I checked the oil and found it to be way overfilled. I know I did not add any oil sine I last changed oil so I drained it and about 2 quarts poured out and was very watery and smelled of gas. I turned the engine over with the starter and it spun up much faster then before which makes sense if that much liquid was in the crankcase.
I re-serviced the crankcase with fresh oil and the engine started normally and ran well.  

How did the gas get into the oil and will it probably occur again?

I read somewhere that the carb float may have a hole and leak gas into the cylinder when engine is shut off.  That makes more sense to me then a cracked ring as the engine runs so well.

Not likely the float is bad but we see a lot of carb inlet needles and/or seats leak allowing gas to enter the crankcase oil.

You can do two things to solve the problem.

1) Rebuild the carb and replace the inlet needle/seat.
2) Install a fuel shut-off valve in the fuel line and shut-off the fuel when you are done using the mower.

The second option is a proven method to preventing the problem, cheap, and something you can do at home in about 5 minutes.  However, you have to remember to shut-off the valve every time you finish using the mower.

You can search You Tube for Briggs carb rebuilding or inlet needle replacement as there are lot of videos for replacing the wore parts.


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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