Gabe,
If you have access (of know someone) who has a CAD program, for an easy degree wheel you can draw one, print it on a large self adhesive label (8.5x11 avery) and stick it a piece of tin (or even cardboard or an old CD if the hole is not too bid). Over the years, i've made a few of these and they work quite well. Heck you can just glue the paper on if you have no label. If you're stuck, drop me a pm and I can email you mine (6") in a pdf or autocad. You could print it off at home. As far as timing, Doordie and Paul are correct. Think that as your piston approaches TDC the sooner the ign fires before the piston gets to TDC, the more advanced it is (the timing), therefore as you reduce to 2.2mm the piston is closer to TDC when the ign fires, hence retarded. Modified 4-strokes like more advance, 2-stokes not necessarily - take a few tests to find the best setting. Although I always thought that retarding was better for bottom end power but likely depends on the engine. Have fun. I have too much snow to test anything now. Rebuild season. Cam.