The YFZ450 has a WR450 exhaust cam. I have heard differant reasons for this from many reliable
sources. Since I am in favor of any increase in power as long it does not sacrifice power elsewhere, I
dont understand any of their reasons. The differance between the WR and the YZ cam is simple. The
WR has the timing mark (where it lines up with the head) moved up (or clockwise) one tooth from the
YZ. This advances the cam when installed by the timing marks in relationship to the YZ cam. The best
way to have the YZ cam is to install the YZ cam. Another cheaper way is to simply retard the exhaust
cam one tooth. In the photo below the Intake cam is at the stock location, the flywheel is at top dead
canter, and the dot shown on the cam sprocket is simply moved up one tooth from the stock location.
When you pull your cam caps off to make this change , be sure to do as I did and drop one of the half
moon rings into the bottom of the engine, so you can spend the next 2 hours digging it out.