Husqvarna / Briggs, Engine pop @ full throttle

[rhelmore]

Husqvarna 2348LS Riding Mower, 48” cut, Endurance Series
Briggs & Stratton 23hp Engine, Model 44L777, Type 1038 B1, Code 071227YG

I was mowing a few days ago and heard the engine sound a soft putt. Then, slowly the putt became a louder more frequent pop. At low idle, the pop cannot be heard. At mid throttle, the pop is soft and less frequent. At full throttle, the pop is louder and more frequent. I replaced both plugs and added fresh fuel. After running engine for a while there was no change. This engine has only 138 hours usage. Any ideas?

Listen for the full throttle pop sound on this video at http://youtu.be/MkJiEGoMdZ8. The video starts with the engine at low idle, then moves to mid throttle and finally full throttle. That’s when you can hear the “pop” toward the end of the video.

Thanks.

Robert

[Mark / Ohio]

Welcome to the forum Robert and thanks for the video. Sure sounds like a misfire for some reason.

At first I thought it might be fuel related since it does it at higher rpm but when you open the throttle it does not sound like there is any stammer like it is starving for fuel. Have you hit anything with the blades that might have partly sheared the flywheel key? Is it using anymore oil then normal?

[rhelmore]

No sir. Absloutely have not hit anything with mower blades. Also, it is not using any oil. Should I do an inspection of the flywheel key?

[Mark / Ohio]

If you didn't catch the blades on anything the key is probably OK. Although that is something easy and cheap to check.

I still have lingering thoughts of something fuel related. Might try to add a tiny bit of choke at wide open throttle and see if the popping goes away. If it does then that could indicate it is running a little lean, some crud in the carb perhaps.

Which brings up another thought. Have you ever changed the fuel filter?

[rhelmore]

I replaced the fuel filter and there was no change. Pulling the choke out less than half way smooths out the engine even at full throttle. I have already removed the carb with manifold and will start the disassembly / inspection / cleaning tonight.

[IdBeDan]

This may sound silly, but my first thought was an exhaust problem. Manifold perhaps? Good Luck