I picked up a bluebird lawn comber c-18 From a hardware store late last year. It was a former rental, and I didn't get a chance to run it until the weather broke here in the north east. I changed the oil, air filter, fresh gas, new plug. The motor smokes (white ) real bad and the plug will foul after about 15 minutes. any Ideas, Should I be ordering a new motor from northern tool ??