I have taken this engine apart and replaced the bent crankshaft. I made sure I set the timing with crankshaft and camshaft correctly, and I made sure I set the ignition air gap correctly. After I mounted it to the mower deck and filled it with oil and gas, I attempted to start it...It didn't start. Instead, the pull cord got ripped from my hand. Does anyone know what could cause this? I had to take the flywheel off before (to replace the crankshaft) and the key looked good. I attempted to start the engine without a blade on; I have heard that some flywheels are light enough to where they need the blade to have enough rotational inertia to get past TDC (this engine has an aluminum flywheel). I want to know if this should be the only cause for this problem or if there could be some other cause (before I buy a $30 blade adapter and a $20 blade).