clutch mod is when you take apart the clutch and theres a spring thats in the shape of a circle with lots of ball bearings in it, you unscrew the spring fro its self and then dump the balls out, then replace every other ball with something lighter than the metal one, some here use rubber tube cut up i myself have tried this but when i tried to take it apart, the spring got deformed and is now useless, but well worth it i hear if you can complete it, i am looking for another route to this now
also ive heard some puch rear sprockets fit and a guy one here will make you custom sprockets if you send him the old one for measurement