More than likely head gasket is blown as PFG56 says. usually will start smoking when load is applied. Also check for being overfull on oil, carbs can leak and drain into crankcase and raise oil level. a lot of times it thins the oil down so much it makes it hard to read on stick. Check air filter for oil as well. If your breather is puking oil it normally will get into air filter as wellMAKE SURE THERE IS NO GAS IN THE OIL. IF IT IS,YOU WILL HAVE TO REBUILD THE CARB AND CHECK THE HEAD GASKET. SOMETIMES ALL THAT GAS AND OIL IN THE CYL. WILL CAUSE THE HEAD GASKET TO BLOW.