Have a Tecumseh 6.5 HP mower. After hitting a stump, the motor began to clank and then died shortly after. I found the keyway had broken, and replaced it. It started up fine but began making that clanking sound immediately, almost like the blade was hitting something, but it is not. The engine runs for about 10 seconds and the keyway breaks again. Have replaced it 3 times and engine still noisy.
Anyone have a suggestion, because everything inside looks fine. Cannot figure out what makes that metallic clanking.

the crank doesn't wobble, and is still straight, and the blade is balanced and is straight? either one of those can get bent, off balanced if something was hit.

A bent crank will not cause a key to shear. If the flywheel nut is torqued properly the key will stop shearing. On the metallic noise, check it out once the engine is not trashing keys. You might want to take the plug out and turn the blade through to try to find the source of the noise. You may have also sheared the blade adaptor key, this can cause some odd noises.

Mike

The sheared blade adapter key will also cause it to shear fly wheel keys left and right. If I had to guess, I would say the problem probably lies in the blade and/or blade adapter.

A bent crank will not cause a key to shear. If the flywheel nut is torqued properly the key will stop shearing. On the metallic noise, check it out once the engine is not trashing keys. You might want to take the plug out and turn the blade through to try to find the source of the noise. You may have also sheared the blade adaptor key, this can cause some odd noises.

Mike
this is what i know... trying to figure out what could be causing the clanking noise. if not internal.

A loose blade will cause this, also.