Here's a Yamaha YZ250F that I built and maintain for a local AMA Pro motocross/supercross rider. The blue line is with a full Big Gun exhaust system, (not my favorite, but it works kinda ok) and a stock engine. The red line is after the addition of camshafts, porting, and high compression piston. (it is stock bore) There's a few other things in the mix as well but I can't give away everything. It has been pulling a lot of holeshots at AMA races and the cheating allegations are always there... we're waiting on someone to throw down the $$ for a protest because it's legal! Factory team type power, without the big cost.