Outdoor Power Equipment and Small Engines - Sputtering lawn mower

Having a problem with my Murray lawn mower with a Briggs & Stratton 4.5 throttle free engine. The lawn mower sputters when stationary or being pushed until it gets to about the last minute of gas then it runs normal without a problem. Before it gets to almost empty, it will barely cut or revs up and then lowers during the whole tank of gas. Any suggestions what could be happening here? Only two years old and wondering should I try to repair it or replace it. BTW, changed out the spark plug.

surging is usually caused by fuel starvation. You probably have a restriction somewhere in the fuel system and the engine is starving. Carburetor is usually the problem.

S/T

Thanks for the quick response. Should I disassemble the carburetor (oh me of limited skills) or add something in the gas to unclog the carb? Not sure I have the original book but I do have the "How to fix just about anything manual". If I can not fix this problem, does it make more economical sense to have it repaired or replaced? Only 2 summer but they are about $150 at Walmart. :)

Actually, it sounds as if it's getting too much gas. I'd have a look at the air filter first off. Take it out and clean it and re-oil it. If this doesn't solve the problem, remove the carb, install a primer check vlave kit and a new diaphragm and see how it goes. It's an easy job and shouldn't set you back more than $10.00 or so.

Thanks guys, I will give those suggestions a try. Afterall, what do I (clumsy fingers) have to lose?

I've had the same problems that have been described here.

One of the gas stations had a summer promotion with ethanol blended gas for the price of regular. Thought it was a great deal! Put some in and while cutting it would sputter and smoke until the last couple minutes, which it would rev up and run fine.

So I went to another station and got regulat unleaded (87 octane) and the problem slowly went away. It took a few minutes to adjust back, but it's running great now!