Engine problems after warmup

Old 04-30-12, 04:48 PM
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Engine problems after warmup

Hi all,

I have an older Snapper lawnmower, probably 1970-1980 not sure. It has a 11hp Briggs and Stratton engine. It seems that it has developed and issue after running. It starts and runs fine for about the first 20 minutes ( I can almost set my watch to it everytime and halfway through the yard) then it decides to fizzle out and die like it has just run out of gas. If I put the throttle all the way down to the lowest idle it will start and run fine at low idle however, as I steadily start increasing the throttle, it speeds up to a point where it just dies at a certain point ( like half throttle). Sometimes if I am patient enough I can increase the throttle so slowly it will hold and get up to speed and stay there but this a slow and tedious process and doesn't always work. Any thoughts as to what would cause this. Thx
Old 04-30-12, 05:17 PM
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If the engine is that old, then it has an older adjustable carburetor. There should be a screw under the carburetor bowl. Unscrew it just 1/8 turn or so and see if it behaves better.
Old 04-30-12, 09:50 PM
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make sure the gas tank cap is vented

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