Briggs and Stratton mower rpm problem


Old 05-07-07, 12:01 PM
Thread Starter
Join Date: Apr 2007
Posts: 9
Briggs and Stratton mower rpm problem


I have a Briggs and Stratton push mower that would not start this season. I emptied the fuel and put new fuel in. I took the carburator off and cleaned it with carburator cleaning spray. Now, it starts just fine, but it revs inappropriately. The rpm's go up and down on a regular cycle, each lasting about 2 seconds, like this: __--__--__--__ It doesn't have a throttle that I can adjust. Does anyone have ideas on what can be done to fix this? I can get the model number and serial number when I get home if it will help.

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Old 05-07-07, 12:54 PM
Join Date: May 2007
Posts: 8
Sounds like a lean surge. Double ck that carb again and use compressed air if available to blow out all of the passages. Ck for any air leaks at gaskets, and torn gaskets.
Old 05-07-07, 02:26 PM
Thread Starter
Join Date: Apr 2007
Posts: 9
Thanks. I'll double check the gaskets. There are only 2 places where air could be getting in, so that shouldn't be too bad. Another thought, I haven't replaced the spark plug. Could that cause the surging rpms?
Old 05-07-07, 05:43 PM
puey61's Avatar
Join Date: Apr 2004
Location: Upstate New York
Posts: 3,224
No, on the spark plug causing the surge (governor hunt). Even though you "cleaned" the carburetor, you still have a fuel starvation issue. Perhaps you can simply get by by doing a better job of cleaning out the main jet (the carburetor bowl nut). The jet has tiny holes in it in order to properly meter the fuel. Use more spray cleaner and compressed air to blow through the tiny holes/passages in the jet. What, specifically, is the spray cleaner you're using? Disregard these steps if you have a diaphragm type carburetor and post back if you, indeed, do! As with any post, the more information you can provide, the better. By all means post back with engine as well as chassis identification numbers.

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