My son has the RTR and we start it no problem on my Starter box which is used for my Pro. You might have to remove one of the shims on the engine mount. I would have to check on his engine, but you don't need to go buying a new flywheel.

Remember, that if you buy a new flywheel and it's too large, you have the risk of it stalling the engine if you land or drive over a large stone.