# Briggs and Stratton Surging Problem.



## Freqflyer (May 30, 2011)

First where do I find engine and carburetor model numbers? It's a 12hp Briggs and Stratton vertical shaft engine on a riding lawnmower. It says I/C Industrial cast iron bore on it.

I replaced the fuel filter, it was flowing slowly. I replaced the gasoline. It has ran long enough that the old gas should be completely out of it. I noticed the carburetor was loose from the engine, so I tightened it up. This helped a lot. Also, it has been overfilled with oil in the past, but it's at the right level now.

Here's the problem. Surging. It will run fine or almost fine with no load on it. It will run and drive at full throttle. It will mow at full throttle but occasionally dies' often enough to make mowing impractical. This occurs worse when it's warm. When you first start it you can mow for maybe 30 minutes without problems. It does start right up when you try and start it.

The governor is bouncing back and forth a lot. If I hold it, then I can get the engine to run well.

What could be the problem? I suspect I need a new gasket where the carburetor and engine meet. Also is there a diaphragm that could have been torn from over filling with oil? I thought that was only on smaller engines.

Any help would be greatly appreciated. 

Also, if I rebuild the carburetor, what should I replace? Is there a kit?

Thanks for your help.


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## 30yearTech (Sep 14, 2006)

The engine model type and code numbers should be either stamped into the blower housing covering the engine, or on a plate riveted to the cover. You may have a worn throttle shaft in your carburetor causing some of your issues, the carburetor may also need some service and of course there could be other things that may need attention as well. If you can find the numbers and post them, they would be very helpful. You will have to look closely as when the numbers are stamped into the housing they are also painted over and hard to see, may be covered my dirt.


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## Freqflyer (May 30, 2011)

I'll look the numbers up tomorrow. 

I have figured out, looking on here that it is a flo-jet carburetor. The one piece I think.


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## Freqflyer (May 30, 2011)

*Model number*

281707-0411-01 90021531


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## usmcgrunt (Sep 16, 2007)

Here is a link to the service manual for your engine.
http://www.mymowerparts.com/pdf/Bri... Single Cylinder L-Head BRIGGS & STRATTON.pdf


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## Freqflyer (May 30, 2011)

I took the carburetor apart and cleaned it. I couldn't get the main jet out to clean. It was stuck, so I sprayed cleaner through it. The throttle bushings were pretty bad. Also, the governor spring was broken. The guy at the parts counter said they don't make the bushings for it anymore. I bought the spring because I noticed that when I held the governor arm in place, the engine ran better. 

It runs well now. Good enough to mow.

thanks for you help.


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