But the engine in our bike is a 4 wheeler engine.
The guy who I sent my head off to specializes in them and actually collaborated with some of the Skorpion performance specialists when they were developing parts for the MZ. It was interesting talking to him.
http://www.kenzcycletech.com/Yamaha%20660%20Raptor.htmI bet if you go to some local meet ups of guys that don't look like mid twenties hipsters, and ride genuinely interesting bikes, they will know a person capable of doing the work. You may even have to drive an hour to find a reputable tuning facility, but someone will be able to get the job done right the first time if you are willing to pay unless you live in the middle of nowhere.