Small Engines (Lawn Mowers, etc.)/small engine


QUESTION: 13.5 ohv Briggs & Stratton 21b807 0239 e1 I have adjusted the valves but the exhaust valve doesn't seem to be opening enough the engine backfires through the intake but for some reason runs at full throttle but it spits and sputters at an idle then dies but starts when you turn the key then dies again

ANSWER: Is the flywheel key sheared?  What are the valve clearance settings?  Is a push rod bent?  Easy way to check a bent push rod it to remove, one at a time, and roll them on a piece of glass...the glass is pretty flat and usually detects if there is a bend in the push rod.


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QUESTION: Push rods are straight valve clearance is.002 inches the engine won't run when the clearance is .005" the intake valve opens just as far as you can open it without it bottoming out but the exhaust valve only moves about 1/8 of an inch

Valve clearance should be .004-.006 for both valves per Briggs specs.

The clearance differece will cause timing (mechanical) issues. How old is the engine?  Is the cam wore that much?  Difficult to check the cam lobes as Briggs does not publish specs on the cam grind.


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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