Like on the new Yamaha WR and as on the Canondale? I read the article in the latest Motorcyclist, but it basically boiled down to 'better power' better mass centralization, yadda yadda. But why does it make more power? Isn't it just as likely that the power is a result of the new valve configuration? And if it is so great, why don't they use this on racebikes?
No_6
First of all, the WR does not have the reverse head, the YZ450 does, which is their flagship race bike that James Stewart will be defending his Supercross championship on. It's head is reversed along with the cylinder slanting rearwards instead of forward to centralize mass and get weight off of the front. The reversed head is done in conjunction with the rear-leaning cyclinder to be able to mount the fuel injection forward and exhaust rearward. The power gains are likely through the reduced friction of 4 valves vs 5, the fuel injection and mapping, lower rotational mass and reduced friction from the offset piston/crank set-up.
You also don't have heat from the exhaust system transferring directly into the radiator and blowing back across the engine, instead it is just swept away. Assuming you aren't riding right behind someone, there should be less dirt sucked into the airbox with it further forward.
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