Re: Help with question
Your question is about the key. If you are unsure about it. You may have never pulled one out before. They are often half moon shaped. Google up woodruff key and there is a host of illistrations and information that may help you in your question about it.
Your sprocket must fit snug though or like it did before, it will destroy the woodruff key in short order.
Look very closely at the grove in the shaft and you should be able to see if your application would take the moon shaped key. Chances are if "they" sell one, its probably the one that fits if you are looking at where you purchased your engine.