Quote:
Originally Posted by Jakobi
If you consider the sole purpose of a powervalve, it is to provide an optimum port size for given rpms. By nature it allows one to change the feel of the bike, but realistically it is there to provide a smaller port at low revs (improving bottom end response), while still opening up to allow max rpm and over-rev.
The transition is where the magic happens. If it opens too soon you can get a dip in power, if it opens too fast you can get a dip/spike. If it opens too late it can cause the bike to feel like it signs off and then hit again. Ideally it will be matched with the jetting, port mapping/timing and ignition to provide the best and smoothest curve through the transition and at part port.
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Understood but what is being understood much better with the new designs is the power valves can be set to progressively open over a wider RPM band. The numbers I have seen is that pre 2015 GasGas and YZ open over 500 RPM while the Beta, KTM, and new Yamaha open over 1500 RPM yielding much smoother power. I actually think Sherco has the answer with the Servo power valve. Now back on topic I'm trying to get input if the 2015 GasGas powervalve redesign has seen an improvement or did they just do a preload adjuster. If they were in doing a redesign I would guess they easily could of improve this.