Briggs surging problem

Tom RS

Member
I have a 12 HP Briggs engine on a garden tractor. Engine dates back to the mid 90's. The speed control works fine at higher speed but as I slow it down toward normal idle the engine speed begins to surge up and down. Seems like the governor is just not able to hold the speed constant. Its getting to the point now that I have to keep the speed up a ways otherwise it will stall out.
I cleaned the grass and crud out of the governor area where the speed control cable connects and it seemed to help but it didn't last long.
I can run the engine fine at slower speed if I hold the throttle linkage still by hand.

Is this an internal governor problem or ?
 
That is common when the spring on the gov rod gets weak and does not hold well any more
 
(quoted from post at 17:29:27 11/11/19) I have a 12 HP Briggs engine on a garden tractor. Engine dates back to the mid 90's. The speed control works fine at higher speed but as I slow it down toward normal idle the engine speed begins to surge up and down. Seems like the governor is just not able to hold the speed constant. Its getting to the point now that I have to keep the speed up a ways otherwise it will stall out.
I cleaned the grass and crud out of the governor area where the speed control cable connects and it seemed to help but it didn't last long.
I can run the engine fine at slower speed if I hold the throttle linkage still by hand.

Is this an internal governor problem or ?

Most likely, it's a carburetor issue.

The idle fuel flow circuit in the carb is gunked up/clogged/restricted and can't flow the fuel needed to keep the engine "fed" at idle.

When the engine (lacking fuel) slows down enough the governor yanks the throttle butterfly open, and the engine reverts to running off of the high speed/load circuit in the carb, then when the governor controls it back to idle it lacks fuel and the cycle repeats.

And repeats.

Fix or replace your carb and the "governor problem" will be gone.
 
Good afternoon: The poster says if he holds the linkage steady by hand, it runs ok at low speeds. To me that is saying the carb low speed parts are ok.

Dennis M. in W. Tenn.
 
Surging is sometimes the result of running too lean, try opening up the low speed adjustment. Have you tried adjusting either screw? Possibly some varnish in a small passageway, put some Seafoam in the gas and run it, after it cleans out you will probably have to readjust the carb.
 
I would look into the carb for sure. The alcohol in the gas ruins aluminum at times.
What I would suggest is to clean the idle circuit by 1 of 2 methods. After a good cleaning with carb cleaner I would try using a set of Torch Tip cleaners. What happens is the alcohol actually swells the aluminum. (white stuff like rust) Carb cleaner wont touch it. This has to be done carefully. Yous like a pipe cleaner. If this doesn't work you will need to run a drill bit in the jet. You need a "Set" of number drills. (unless you have the jet measurement).

Good luck, neither is such a bad job.
 
Warped upper body , gets feeler gage and test the mating bowl body to the upper body. .
Probably can seal inexpensive with permatex number 2 and let set over night to seal
 

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