The first thing that you could do is check your crankcase for holes that could cause the compressed air to leak right out. If you have no succes, take the spark plug out and squirt a couple shots of motor oil into the cylinder and try cranking it over. If that doesn't work, you should probably check your vlves to make sure that the seats are in good shape. If they're not, remove them and re-seat them with a suction cup and some valve joint compound (e-mail for complete instructions). If all else fails, you could be having problems with your piston rings being worn out. There are a couple of signs that this is your problem. 1. your motor is burning more oil than usual. 2. your motor seems to start hard. 3. your motor gets little to no compression. Compression loss is a common problem in small engines, and these remedies should work for you.