Mike; When setting the timing on Bs,Cs, etc., I bring #1 piston to top dead center, be sure both valves are closed or you will be 180 degrees out, and match the teeth on the mag with the rotor aligned with #1 plug wire tower on the cap. It's the low tech way I know, but, works for me. The engine should start with timimg at Top Dead Center. Once running I correct timing with a timing light and turning the magneto to bring timing to spec. Hope this helps.