What causes the Oil Leak???<<<----------
 

Please help! I haven't rode in 3 months, took a while to start up, I changed the oil and gas, now I have a leak under where the exhaust pipe connects to the cylinder and TONS on white smoke comes out? When I checked out oil levels again, it was basically empty! Any advice would be great thanks!

was it running good three months ago?white smoke is a sign of bad rings

Looks like an air cooled 4 stroke. Lot of smoke is an indication of oil being burned in the combustion chamber. The # ONE cause I've seen is over filling the crank case with oil.
Double check the procedure and make sure the oil level is correct.

It actually blew up, I found the piston and cylinder thrashed. I replaced the whole top end, piston, rings, top and bottom cylinder. My oil level is always good, even checked the valves with clearance. I'm lost, will check rings again...

Sitting for a while could dry the cylinder out a ring could bind up on dry start and crack , check the clocking on the ring gaps make sure there not lined up and do a compression test.