Dynamo rotor

I removed the dynamo rotor today to replace the starter clutch and realized the woodruff key is missing. Is this a common problem? Sure this is the reason the starter doesn't work. Can I replace the key with one from the local hardware store?

What bike is it? And not nessasarilly the reason it doesnt work, does the starter motor turn? Is the starter clutch grabbing etc?

76 kz900. Starter spins and gear spins when I push the starter button but the gear and rotor spins i think because the woodruff key is gone.( rotor and gear spins on crank. )

Woodruff Key from Z1 Enterprises

Good Fortune!

Well put a woodruff key on it, and a little blue locktite on the end of the crank and the crank bolt and torque to spec (something like 20ft lbs torque iirc?)