If it is an early model, they had trouble with the flared tubing to the carburetor breaking. This would cause a no start situation, bit you should smell propane. Check the basics first. This is a 4 stroke motor, the same as any other than the fuel. Check for spark by using a tester of ground it to the block and pull it. Ive heard of the kill switches wearing out, but havent seen it first hand. There really isnt much to these, but I would start with checking fuel and spark