I build my own magnetos from parts. Start with a good Fairbanks Morse body and go from there. They usually work great (strong spark, etc.) . . . however, since it's the most "misunderstood" aspect of an engine build (compared to setting valves, carb jetting, etc.) you naturally suspect it's the problem/reason your bike won't start. Whenever I think my magneto is the problem, I send it to Rudy Calin in Minnesota (Rebuilt Mags) to get it checked out . . .
Rudy also replaced my condenser with the slightly snappier FM SXY2433 mfd. I looked through my box of mag parts, and found I already had one . . . by Colt Industries (who purchased Fairbanks Morse Company) Rudy also recharged my magnets ! Old Sparky Comes Alive !
(see my condenser output TECH chart soon)
I prefer these black caps with the "lightning bolt" or the old-time factory-made FM magneto caps. The clear caps are handy to view your points breaking(or arcing), but they can allow sunlight to heat up condensation and moisture inside - also, I think they're just plastic? Rudy has really nice & heavy cover gaskets available too . . . www.rebuiltmags.com