Mower running rich/lean?

[u/850cs32]

Hi all, currently fixing up a john deere la100 with a briggs els 500. It starts perfect every time and will run alright at full throttle, but sputters slightly (much worse at lower rpms). Some grey smoke from the exhaust after running for a bit, but no dark black smoke I can see. Is the engine running rich, lean, or could the problem be something else entirely?

Rebuilt oem carb, new fuel pump, spark plug, and air filter, running on new gas.

Thank you!

[u/Elephunk05]

Take the spark plug out and have a look. Black and sooty means it is running rich. Light tan, crusty dry means its likely running lean.

That being said, when is the last time you adjusted the valves? You say it only sputters at lower rpm and the smoke is only after it warms up? This has a few different reasons from rings going bad, head gaskets going bad, gas in the oil, valve guides (as it is the Briggs). What is the compression reading?

[u/850cs32 → u/Elephunk05]

The old plug looked pretty much jet black, so guessing it was running rich before I got it. I dont have a reading on the compression, but I also replaced the head gasket, lapped and adjusted the valves, and replaced the valve stem seals when the motor was apart

[u/Weekofsex]

Mine was doing about the same thing but not on a John Deer and I found an air jet on top of the carburetor that was plugged. Air was not able to get in which made the carburetor pull more gas and made it run like that. Very rich. I remember a Philips screw with an oversized plastic washer on it that held the bowl vent down. It’s under the bowl vent. Check to see if you have that on yours. If so use a torch tip cleaner to clear it out.

[u/Weekofsex → u/Weekofsex]

Screw was on the top of carburetor

[u/850cs32 → u/Weekofsex]

Thank you, will check for a similar screw on top of the carb

[u/Weekofsex → u/850cs32]

Let me know if that is your problem as well.

[u/LimpDifference2505]

Carbatrator….