- Wed Aug 08, 2012 10:33 am
#16206
This is just like the magneto on my 1953 Model G was before i had it rebuilt. What happens after 50 years or so is that the shellac or whatever they used as insulation on the windings is cracking. When hot the metal expands and the cracks open, leaving uninsulated gaps. Then you get short circuits and no spark. When it has cooled down it may work fine for a while again. -.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.
I got a very educational demonstration of this when I handed my magneto over to the workshop. He put it in a test bench, hooked it up to an electric motor and ran it at about 1500 rpm. It sparked happily away across a 6 mm spark gap. Then, as it was running, he heated the magneto body with a heat gun, and suddenly it started failing, first intermittently, then completely. At that point it was just not too hot to put your hand on it. -.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.
I think the only real and permanent solution to this is a complete rewinding and rebuild. There may be other ways, but it will have to come apart anyway, and I doubt that it will be much cheaper to do it "almost" than completely. -.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.
Good luck! Regards, Anders F. R.
