I did it on my 1998 EC250SM conversion. http://www.gasgasrider.org/forum/showpost.php?p=33295&postcount=2
Had to do a little grinding on the clutch master. I also had to pull the swing
arm bolt and slid the swing arm back to get the sprocket past the plastic
swing arm guard. But it fit and has worked for the past two years or so.
Jeff