you have to use an oxy to heat the sproket up, then very carefully split the sproket with a cold chisel and it should come off, to get the new one on you will have to cool the shaft down to shrink the metal it will be a tight fit so a big hammer might do the job, but if not done righs can be very expensive to fix so it is better to get a dealer to do the replacement.
butch
March 2005