What is involved with swaping out the rotary disc? Can anybody do this or should I have it done? I have better than average mechanical skills but I dont want to calibrate this wrong. Just wondering if anyone has experince with this? ANy help is appreciated.

Buy a race manuel and it takes you through it step buy step. You will need a degree wheel. Its pretty easy to do.

to pick a valve is up to you I suggest 5deg max difference. I have done this several times with no special tools. Remove carbs and spark plugs. remove rotary valve cover. now use a pencil through plug hole to find an approx tdc (top dead center) on your mag side cylinder. now remove clutch cover and grab clutch and rotate back and fourth just a few degrees to find your exact tdc mag side. One your sure you have figgured out the feel of the crank and know you there. Take the rotary valve of choice line up the valve just where the cut out starts on the say left. Line that up with a notch on the upper left side of the crank case. which when your done the port on the crankcase mag side should be starting to open. U can flip the valve over so a differnent spline lines up better than the other side... splines are can be triccky to get the valve on. Note.. the hardest part I have here is describing the valve its self and where u line the crank case notch to on the valve. I wish I could draww a picture.