secret gizmo

I dont know what it is but has anyone seen a close up shot of a factory yz426 with a funny looking canister attached to the exhaust header?? I think it might have something to do with crank-case pressure, but I'm not sure. If thats the case what advantage would there be in running it to the exhaust instead of straight to the atmosphere? If it makes such a differance in horsepower why hasn't anyone mentioned it? I might just think about it some more.


EXUP valve, this is used to make power in a broader range, from what I've heard. R1's have them.The engines on the race bikes are also wet sump.


00 WZ400

01 Yamaha Raptor

99 Kawasaki ZRX1100

99 Yamaha Warrior

It changes the amount of backpressure depending on the amount of flow creating the maximum amount of power throught the throttle range.


This idea was first put into mass production on the yamaha two stroke RD/RZ series of road bike, there were "bobbins" fitted in front of each exhaust manifold that lifted or fell depending on the RPM of the engine. This meant that the back pressure was cutomisable and in tune with the motor at any given rev range, giving more low/mid range power without any loss at the top.

On their four strokes they used the same theory (starting with the FZR1000 EXhaust Ultimate Power) except they put a valve/butterfly in the exhaust just after where the four downpipes meet.

So how do we get one?

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