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Rick, Factory Authorized Trainer
Category: Small Engine
Satisfied Customers: 8063
Experience:  Outdoor Power Equipment technical trainer since 1990, covering eight states.
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I have a Briggs and Stratton 3.75 HP Sprint II push lawn mower. Model

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I have a Briggs and Stratton 3.75 HP Sprint II push lawn mower.
Model #: 9L902 Type: 0305 E1, Code: 05111152

Problem: When running, the engine tends to rebs up then slows down. There's an adjustment lever right above the air filter with one larger spring and a smaller one on top. (Is that the correct # XXXXX springs?) When I move the lever to the left it speeds up and to the right it'll slow down to where it might stop)

What's the problem and how might I fix it.
How old is the fuel in the tank? Was there fuel older than three weeks in it recently?
Customer: replied 8 years ago.

The fuel is fairly new. I believe it falls within your time frame. I've used it my other lawn mower and it works fine.


I've removed the gas tank and cleaned it out. I have also cleaned the carborator. New spark plug. checked the muffler and after taking if off, I blew air through it. It's the orginial, and I can't remember how old the mower is.


I was thinking of the 3 things the engine needs, fuel, a spark and air....

You got that right. As long as compression is in the mix too...Smile


If you're surging, that's usually either a weak or deformed governor spring or a plugged carburetor. That a late 2005 engine, probably on an '06 mower. Has the carburetor ever been rebuilt?

Customer: replied 8 years ago.
No, the carboretor has not been rebuilt to my knowlegde. I'd like to investigate the "governor spring". Can you provide a clear drawing to where/how these springs are attached? I'm thinking that pushing the mower up under low pine tree branches could have either displaced them or stretch them. What you think? I assume these springs can be purchased at a Brigg and Stratton repair shop?

Yes, you can get them at an local Briggs dealer. Here's a parts illustration:


Rick and 2 other Small Engine Specialists are ready to help you
Customer: replied 8 years ago.
Thank You Rick G, You've been most helpful.