Dolly

TEAM MULE 610! My Mule is an old beast. bought used. 10 years now never a problem. Plowing snow off steep driveway this morning however in Wisconsin.. on way up long hill Mule starts blowing billowing cloud of smoke out of exhaust. I stop let it idle and it gradually clears up. Try again.. same result. Ready to pull into garage and DIY fix. Anybody seen this? fixed this? Carburetor? Piston Rings? Best Wishes!