Engine Engine rough and smokes

[crobar13]

I just acquired an MTD riding mower Model 13AN678G022 with a Briggs 313777 OHV engine. It smokes and runs rough. It also does not seem to come up to full speed. The throttle is adjusted properly. The oil was overfilled, so I drained it (seemed very thin) and replaced with fresh 30 W and also changed the oil filter. I still have the smoking and rough running problem. Tomorrow I will check and see if the choke is stuck closed , but I don't think this is the problem, as this doesn't account for the smoke. The dipstick is sealing properly. Any suggestions for diagnosing this problem?
Thanks Robert

 

[ILENGINE]

The main question is what color is the smoke. Black means running rich, blue means oil If black most likely need to remove, clean and install carb kit. if blue could be blown head gasket, or valve issues.

 

[bt3]

Smoke can also be an oil overfill issue. If the oil is thin, do you smell GAS in the oil? Your needle valve and float in the Carb may be sticking and allowing gas into the crankcase. If this is happening, it's a fairly dangerous situation, and you need to remedy it quickly. I have this issue at present with my Snapper Wisconsin Robin Commercial engine. I have ordered the Carb kit for repair.

Some may say it could be bad piston rings, or valves/gasket issues, but the most likely candidate for smoke based on what you have said is overfill of oil, and/or gas leaking into the crankcase and thinning out the oil and thus overfilling the crankcase with gas filled oil generating a lot of smoke out the exhaust. It can sometimes be temporarily remedied by putting in a shutoff valve in the fuel supply line for when the engine is not running, but if this truly is the case, you need to rebuild that Carb ASAP. I say this because you commented the "Oil seemed very thin". Worth investigating.

Good luck.