Seems to me that the arm can only go on in one position.. Logically the valve would be in the closed ( down) postion at idle or dead engine and open (in the up position) at high RPM. Does this bike have the boost ports connected to the round gears? My 91 had them, I ground the teeth off the gears, for a little harder hit.. I also had one of those phillips head screws back out on the clutch side and make its way into the tranny. I found metal flakes stuck to the drain magnet.. I tore the engine down and found the rest in the tranny.. Took me a while to figure out just where the metal came from as it was smashed up pretty good.. On re-assembly I peened the edge of the screws.
I also seem to remember some very small marks on the gears ..
zilla