Powervalve Orientation

Just FYI if you are interested,

At high revs (not throttle to be pedantic ) you will have the maximum exhaust port exposed and the port sealed off from the side of cylinder box.

At lower revs (along with lowering the effective exhaust port) this side box opens to disrupte the returning pipe wave, which at low revs is at the wrong time. It is often claimed this box adds volume to the pipe. Strictly it does, but it is not beneficial for that reason. It just needs to be big enough to absorb the wave enough. That way the pipe can be tuned with respect to more top and not suffer a strong mis-timed return wave, or scavenge for that matter.
But those ports left and right are open once the pv is fully openend. Shouldn?t they be closed then? Am I missunderstanding which ports are open or closed? I am generally speaking about the 2 little ports besides the exhaust port in the cylinder that you can see from the inside. :D
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So ports left and right of main exhaust are maximising the port area at full revs.

Try to imagine you want to get the exhaust gas out as quick as possible at top of stroke at full noise.
At lower revs that would promote short ccting.

Brain is full of different systems from previous bikes, but the additional opening to the closed box on side of cylinder should be a low Rev thing.