What does the PV chamber do?

[stay_upright]

Could some-one explain how the PV cover/chamber on the LH side of the engine works

Also what is the idea behind the two additional rotary PV 'valves'

[socalscott]

Could some-one explain how the PV cover/chamber on the LH side of the engine works

The left rotary PV when closed(hi compression) diverts exhaust to the
chamber. Effectively creating a larger volume head pipe segment.

Also what is the idea behind the two additional rotary PV 'valves'

Wider port area. They provide hi-compression up to mid rpm and lo-compression from mid on up. There's an ideal point for them to open. It's where hp can take over just as bhp peaks. We can play with that point with
PV gov. spring pre-load or different spring rates.

[mountain thumper]

are you saying you can "tune" the pv

[JoshP]

Thrusty does make a tunable PV cover for the euro's. With some fancy on the fly tuning dial. Almost seems like cheating.

[Skidad]

Thrusty adjustable power valve

http://www.trialendurodirect.com/pro...Cover_139.html

Also see the pics I posted above for this.


Skidad in MA

[JoshP]

Now all your need is the GasGas Skidad. Sorry had to say it.

[nhrider]

Originally Posted by JoshP

Now all your need is the GasGas Skidad. Sorry had to say it.

He's trying! Skidad, don't worry something will come up...

[asshat]

I just bought an 2002 xc 250 in close to mint shape, around 25 hrs. But my older ride is a ATK lq 260 with a Rotax in it.
The rotax used has an adjustable power valve. I must say it is one of the cooler things about the bike. The engine is great. Not a powerhouse but for my lightweight, it goes well. Ultimately reliable. In the spring I crank the PV spring tension tighter to open later, and its electric. As it dries towards summer I set it mid depending on traction required, if it's hard, I just set her to open earlier.
Why they all don't do this I have no Idea. Sounds like a decent way to take the edge off of those XC's,DE's and MC's people out here in the East are running. Cheaper than an expanded pv cover/Throttle Cam/Flywheel weight/ EC ignition combo. And once installed way easier to go back and forth. Simply bend over and crank the screw.
Anyone running one? How easy to install?

I am asshat

[stay_upright]

So the chamber (LHS cover) acts as sort of a mini expansion pipe then?

i.e. exhaust gas goes in - reflects off a surface and is pushed back into the cylinder?

[2 strokes 4 life]

They way i look at it is Vboost like on a Yamaha Vmax almost. It opens after a serten amount of exhaust gasses that pass through it and then it whacks open and lets more exhaust out.