take the master link off, measure how long you need the chain to be, then you can either grind, or press the pin out of the link where you need to shorten it. i use a chain tool to do mine. when you put it back together, its REAL important to look at the safety clip. one side of it is kinda rounded on the edges while the other side has more square edges. make sure the square edge side faces out and that the round end of the clip faces the direction of chain travel. if you dont do this, you master link will come apart on you at some time. not a good thing at high speed.