I have a B&S 20 hp OHV motor on a small yard tractor.

Starts fine. Runs fair. When deck is on and it's challenged, the motor wants to die. Or when just driving along (it's hydrostat) and I hit the pedal a bit harder and turn hard, it will try and die.

When it does try to die, it will spit out a bunch of white smoke.

What's my best bet to try first? Pull the carb and soak/clean? Or could it be something else?

Thanks.

I'm guessing you have to much oil in it, hence the white smoke, second if its a twin cylinder engine I would guess one of the plugs is fouled, hence the lack of power.

Another thought on the oil, if it appears to be over filled smell it and see it if doesn't smell of gas, the float in the carburetor could be sticking and letting excess gas to be dumped into the engine ending up in the crank case.

Yes. Check oil level. They are sensitive to overfill.

And change out the inline fuel filter. Could be clogged or partially restricted.

White smoke only happens when the thing nearly dies.

Can be running fine for 20-30 minutes. Then when it gets challenged it bogs and then will spit white smoke while it's coming "back to life", so to speak.

I'm betting it's oil related.

But, it could be the seat switch under the seat trying to kill it because it's not making good contact. Mine was doing the try to die thing, and I unplugged that switch and cleaned it good, sprayed WD40 on both plugs and put it back.

No more issue for me.

Is this a single cylinder or a twin cylinder engine?

I'm not familiar with that particular engine but it could be tight valves.

Get it sorted, Matthew?

I have not yet.

Planning on replacing plugs.

Then jump the seat switch.

Finally I am planning on pulling the carb and cleaning it up and see if that helps.