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mike_sdak

briggs throttle shaft question

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mike_sdak

Hello. All this snowblowing is giving me time to notice a few nagging issues....

When I am running, the throttle shaft on the carb vibrates (rotates a part of a revolution back and forth) quite a bit, like hundreds of times per minute. If I hold the throttle shaft steady, the revs drop quite a bit, but the engine runs OK.

Is this normal, or a very worn throttle shaft?

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HubbardRA

If the throttle pulsates fast then slower, then fast again, etc. in a rhythmic fashion, then the carb is out of adjustment. Just turn the main jet adjustment till it smooths out. I have re-adjusted many carbs to eliminate the pulsation, especially when it is a neighbor's mower and I have to listen to that the whole time he mows his lawn. LOL

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mike_sdak

I think I had better deal with the throttle shaft. There is a slight amount of lateral play. However, when adjusting the needles, I closed the idle valve entirely, without making it stumble.

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AcFordHawk

Mike, had similar indications on a couple 12.5 Briggs, the shaft had worn enough through use and age to cause an air leak and tuning was not possible. They seemed to run okay at full throttle but idling was not the best. Same indications you mention, lots of small rotation and some lateral play. Put new shafts on and able to idle and seem to run better at full throttle.

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