# Sputtering at full throttle



## spcchap (Feb 7, 2021)

Hey everyone,

New to the forum. I recently rebuilt the B&S 14.5 HP engine (model # 287707 1255-E1) on my Poulan HD145H42H lawn tractor. Everything is fine except when I go full throttle, the engine sputters and acts like it misses. It purrs at lower throttle. It's almost like it's starved for air or fuel. When the blades are engaged, it works just fine at full throttle.

I've got a new spark plug installed, set with the proper air gap. I also verified all fuel lines are clear and gas is flowing (gravity fed). The carburetor is new (I did buy a knock-off, not the Walbro brand that was original to the mower). Thinking maybe it was a bad carburetor, I swapped it with another Chinese knock-off carburetor -- same problem. The valve clearances are set correctly and the flywheel key is intact.

There are no obstructions to the airflow, and I have run the engine with and without the air cleaner to test. I also installed a new magneto.

I feel like I've thrown everything at this problem. Any other ideas? Thanks in advance!


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## Bob Driver (Nov 1, 2017)

So you're saying it runs fine at an idle and under a load (blades engaged)? How does it act with a little choke applied?


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## spcchap (Feb 7, 2021)

Sorry for the late response. It still sputters on choke. I also replaced the breather valve. It seems to improve a little after I run the engine under load for a while (mowing for 5-10 minutes).


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