You're wrong KRANNIE. I was quoting an article published in Dirt Bike Magazine. Not true at all, check the part numbers. The piston, head, cams, crankshaft, and flywheel are the same on the 2015 WR250F and YZ250FX. In fact, the piston and head are the same between a YZF, WRF, & YZ250FX. The WR250FX and YZFX share the same transmission too. My '15 WR250F with the comp kit, remapping, and a Q4 muffler, is faster than a stock YZ250FX. Not really a pile of work IMO, and not a surprise considering two bikes are mechanically the same engine. Most of the magazines are knee jerk experts, and probably read the "YZ" on the YZ250FX's decals and then automatically assumed it is a YZF with changes with minimal relationship to a WR250F. The real story, is that a FX is basically a WR without lights, but with stiffer suspension and some detail changes. Every article I have read says the YZ and YZFX are the exact same motor accept for the ECU and transmission ratios, and that the WR has lower compression, and a different head and cams. You are saying the YZFX is a WR motor with a different ECU.....with the only difference from the YZ motor is the camset. I cannot find any parts fiche info on the YZ250FX or the WR250f to verfiy this. Where did you find this info.