if you are static timing, you can make a test light for about three bucks, that really makes it a million times easier. i used to always do it with a probe-style 12V test lamp, until i made something better.
go to autozone or napa or whatever, and buy a simple 12V lightbulb socket, like the type used for turn signals. buy two alligator clips, and if they don't come with wire attached, buy a small piece of that as well. wire the alligator clips to either side of the light socket, and then simply clip one to ground, and one to your points you are setting. this way, the bulb is hanging right in front of the timing marks, and you can get it perfect. this really helps on the twins, where the points are up above the stator and timing marks, but it still works great for the 550 and 750 as well.
might not solve your timing problems, but it will certainly improve its accuracy.
