Sounds like one of two things I can think of right off,your float in carburetor could have stuck and filled crancase with gas so after it turns a couple times the pressure won't let it spin any more-check the oil(and smell it).If this is the case drain oil,fill with new and either have carb worked on or put an inline shutoff in your fuel line and turn off with not in use.
Second thing could be your engine timing is off.
Third is someone ran it out of oil and pretty much toasted your engine-had a customer do that once.
Bob, April 2012
