Firstly we are here to help. There is NO woodruff key on the crank. The generator assembly simply locks itself on the taper of the crank. I am unsure exactly what you are looking at.
I have many spares here and i am sure i can help you out.
Is yours a B1/B2 model? looks B2 to me Was it the original exhaust you tried to get repaired? They normally only lasted 2 or 3 years.
I have sent you my number in a PM.