its quite easy - remove the oil injection pump from side of casing and block (pre-mix only now), got some custom made reed valves, custom port & polishing, nikoseeled barrels, carbies were modified as per the Yamaha factory racing manual and got some custom made pipes that are a original 80´s race design from Dennis Foran. My TZR (88/89 hybrid) now puts out nearly 70HP at the rear wheels and revs all the way 13,000rpm. It lifts the front in every gear up to fourth. Mind you i have spent a fortune on this bike. Selling it now if anyone is interested. Its a custom metallic green now and everything alloy is polished and machined to lose weight. It weighs under 100kg wet!