I had to buy a new 10 tooth sprocket for my engine. when the new one arrived, it fit very loose. Called up the company and was told to try it anyway...that's all they sell. Needless to say i did try it, and now the little key, that fits in the groove of the sprocket is gone. My question is this..that little half moon piece on metal they sell, is that what i need to get to replace what I lost on the shaft. Thanks for any help.