small techusa enigine repair?

i have a small techumsa engine on my go kart and i had just takin it out of storage in my back yard and covered with tarp when i uncovered it and started it up it sounded great then while i was driving it for after about ten minutes i herd a rattling then a huge cloud of gray smoke came out of the enigine then i checked the oil and it was good then i tried to start it but there was no tension when i attempted to pull the starter cord what happened?

Blake Theby
October 2008