I've reset lots of power valves for folks who have taken theirs apart, and not paid attention. I've even had folks bring me their cylinder at races as they could not get them set properly. If I have time, I'll write a step-by-step instruction sheet on how to go about removing and reinstalling the power vavles. However, if you can't wait, take a video camera, set it up on the bench, and video the removal process. The brief removal instructions after removing the cylinder are as follows:
1. remove the two bolts from the exhaust ramp, and the one bolt from the rack (this is the long shaft that engages the arms sticking out of the engine.
2. remove the idle gear on the opposite side of the rack shaft (one barrel has two shafts next to each other. The second shaft is an idler gear that simply reverses the direction of the barrel.
3. pull both barrels out about 1 inch, and pull the rack out of the cylinder.
4. remove both barrels and exhaust ramp.
5. sometimes, the barrel holes will need to be cleaned. If you don't have a dremil tool, just tape 120 grit paper to a 3/8 drill bit with the grit side out. Take several wraps of paper on the bit so you'll have something to tear off if the paper gets clogged.
6. rinse the cylinder.
On installation, the trick is to leave the bolts out of the exhaust ramp until you have the barrels engaged in place and timed. Take lots of pictures before you disassemble, especially looking into the exhaust port while actuating the power valve.
I'll be servicing mine soon, so will take a few extra hours and develop detailed instructions.
Rick