You've searched and found.......what?
I got 10 hits with a search for 'radvalve' on this board.
Also, the 'Every kdx rider should read...' thread stuck to the top of this board links you to CDave's site. He has radvalve info listed there.
IMO, it's less than useless considering your other reedvalve choices. Its effect is minimal, the reeds don't last for diddle.
**note** This from a biased point of view. I've compared like bikes with/without. I've seen what boyesen reeds look like after a year's use (fried..) and other reedblock mfgs reeds were perfect. I've compared the radvalve to what I've got now. The radvalve was the loser.
Biased? You bet!
With reason? You bet!
Wibby: On the peak this saturday?