Briggs/Stratton motor racing after warmup


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Old 07-03-10, 09:40 AM
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Briggs/Stratton motor racing after warmup

As my name implies, I am a noob when it comes to stuff like this, but I’d like to have a go at fixing this myself if it‘s not too complicated, so here goes…..please excuse any goofs, wrong terminology, etc…

I have a Craftsman riding mower with a 15HP Briggs & Stratton Model 28N707 Type 0171-01 motor that has recently started racing after it warms up. It is most pronounced when the throttle control is in the “fast” position and there is a reduction in load, like when I start going down a hill, or transition from grass to flat pavement.

I looked at the governor arm while the motor was racing, and it was in the closed position. With the motor off and the throttle control in the “fast“ position, there seems to be good spring tension, and the governor arm is pulled firmly back to the open position.

I set the fuel mix and idle speed screws according to the Craftsman owner’s manual. When I hold the throttle lever against the idle speed screw and tighten the screw, it runs smoothly (but too fast). When I loosen it, it runs rough, but doesn‘t slow down very much.

My air filter is pretty filthy, and I can’t remember when I last replaced it, so I ran the motor without it to see if there was any difference, but it didn’t change anything.

So………what to do now? Any ideas?
 
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Old 07-03-10, 09:00 PM
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Just for a goof, look in the carb to verify the throttle plate is still there,, I've seen a couple with this problem, but can't remember the #'s... At least it doesen't cost anything to look,, Right???? Just a thought.... Roger
 
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Old 07-04-10, 09:44 AM
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Originally Posted by hopkinsr2 View Post
Just for a goof, look in the carb to verify the throttle plate is still there,, I've seen a couple with this problem, but can't remember the #'s... At least it doesen't cost anything to look,, Right???? Just a thought.... Roger
Thanks for the reply. I just took a look. The throttle plate is still there, and there is nothing preventing it from closing properly.
 
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Old 07-04-10, 12:04 PM
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I noticed the fuel filter was full of dirt, so I cleaned it. Runs fine now.

I don't know why this fixed it, but it did. I thought if fuel wasn't getting through, it would stall instead of racing. Maybe someone could fill me in.
 
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Old 07-05-10, 11:26 PM
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I suspect it is coincidence... cleaning the fuel filter shouldn't keep it from racing.
 
 

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