i need to get more clearance between my chain and starter housing so I want to try using a 21 tooth sprocket instead of the 23. I've already got a 21 but it's the old style. i've already put a 49 tooth sprocket on the back so I'm hoping i'll still have some top end left.Gerry said:I guess so. At least it works the other way round. But why do you want to use it that way?