My 10 year old son has a raptor 80 that is getting boring to him. He is not big enough for a larger bike yet but could handle the increase in performance. So I have come across a YFM 100 Champ motor which is supposedly the same motor as the raptor 80 motor just higher displacement. My question is if I changed the jug, piston and head from the YFM 100 motor to the Raptor 80 motor where should I start on jetting with the Raptor 80 carb? It will have a factory replacement K&N with the airbox intact and a custom pipe from Raptor80Racing.com. Is the jug, piston and head a direct replacement? Also does anyone have directions to take the 4th gear out of the YFM 100 motor and install it in the Raptor 80 motor?[img]i/expressions/face-icon-small-confused.gif[/img]

It would be easier to just swap motors. Then you would have the fourth gear and the bigger engine. The top end is a bolt on but you should use the jug, piston, and head from the 100. On the jetting, I'd go up a couple on the main and get it going before I worried to much about fine tuning.

It may be easier to swap but the 80 engine is in better condition. So is the crank the same in both engines? Does anyone have the parts list and directions on how to add the 4th gear to the 80 motor?