Why a flywheel weight? Defeatng the purpose of installing the 06 cdi.Not in the least. I have a GYT-R off-road flywheel on my '06, and if anything, it pulls harder at low speed with it than without it. I'll guaranty there's no loss of performance. As was pointed out, the quad engine is a low power version of the WR. It's down about 8hp to the YZ, and comes with a flywheel 3 times the size of the YZ's flywheel. The YZ450 flywheel is smaller than the gas cap, and weighs next to nothing.