Is there a standard size for the crankshaft sprocket on the high gear side? I am having a spare motor rebuilt and I need to specify the number of teeth. My mag sprocket has 16; it seems to me that the crankshaft should be the same. I can see no way of counting the teeth on the motor I have in the bike at present. The high gear drum and mag drive sprocket seem at a glance to compensate for each other. Can anyone help please?