Mower runs great after new carb, and then sputters and backfires next cut.

[Dan357]

Hello,
I have a 16HP 42" Craftsman Lawn Tractor, 6 speed

B&S 31C707-0230-E1

It was running rough, and I bought a new carb from Amazon ($30) and put it on, the engine ran great, I cut the grass, and it never sounded better.

Next week, started it up, and it sputters, backfires, and runs rough when it gets warmed up. The only adjustment I see is the air/fuel mixture, and I marked it with a paint pen when I put it on, but had no need to adjust it. - One more detail, on the second startup, it started, but was acting like it was getting very little fuel, would not rev up. I checked the gas cap, pulled the hose, popped on a new fuel filter (Inline) and it started up better, but popping and backfiring.


Any thoughts of what may be going on?
Thank you.
Dan

 

[sgkent]

check the oil level to be sure that gas hasn't drained into the oil. Then check the choke to see if it is stuck.

 

[Dan357]

check the oil level to be sure that gas hasn't drained into the oil. Then check the choke to see if it is stuck.

Thank you, will check when the rain stops.

 

[Dan357]

Hello
Gas has drained into the oil and the choke was getting stuck. I changed the oil, worked and lubed the choke lever, and finally, tested the fuel shut off solenoid.
Started it up, still popping and slightly backfire.

smooths out more when the blades are engaged

Dan

 

[sgkent]

so the problem is related to the carb unless your engine is of a style where a perforated fuel pump diaphragm would let gas into the crankcase. when there is gas in the crankcase the fumes make the engine run too rich, and the lack of lubrication will destroy the engine. Beyond that you have to figure how the gas is getting into the crankcase to fix it.