ahh the same thing happned to me with my first .12 engine. because its new it will be tight after it breaks in it will become much more easier. when it gets stuck simply get a flathead screwdriver and flip the car over and use the screwdriver as a lever and turn the fly wheel, that will make it so you can turn the engine over.

some advice, once you have done that keep on trying to start it, once you start it dont stop until you have run a whole tank of fuel, once a tank is through keep on running it and it will eventually loosten up and be much eaiser to use. hope this helps