Small Engines (Lawn Mowers, etc.)/throttle fluctuation


TF wrote at 2013-04-10 11:34:23
Most small mower engines incorporate a simple speed/load governor which opens or closes the throttle depending on engine load. The mechanism comprises of a vane/flap which is connected via a spindle and spring to the throttle butterfly. Air pressure from the engine cooling fan acts on the vane as the engine speeds up closing the throttle whilst the balancing spring is trying to keep the throttle open. When the balance is set correctly the mechanism will keep the engine running at a constant steady speed under most load conditions. This mechanism normally has a clamp for adjustment. Fluctuation usually occurs when the balance is not set correctly. By slackening the clamp and adjusting by small degrees you should be able to get the balance right. Be warned this can be a fiddle and a bit frustrating.

Hope this helps TF

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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