Sr1 magneto

[willowbedone]

Help my g80 starts when cold then will not when hot I guess it's the magneto ? .Does anyone know what the resistance on the coil winding should be And where I could purchase a new one Or get it rewound locally to Hastings
Thanks Ian

[Groily]

In round numbers, about 5500 to 6500 ohms from HT take off to earth / mag body Might find a rewind on e-bay if you look, from a good uk source.
Might also be worth thinking 'condenser'. That's cheap and easy . . .

[willowbedone]

Thanks for reply mines reading 7500 ohms What should the condenser read

[Groily]

7500 ohms is likely an OK reading - depends a lot on the winding 'recipe' when the coil was done. Open Line, Mega Ohms or Infinity is what you DON'T want! Key Q is what it's like hot, under running conditions, but basic continuity is a good start.

Condenser ought to show a capacitance of probably 0.22 to 0.3 micro-farad depending on what's been slotted in. It's not critical to the nth decimal point. That is measured from the tail wire to the metal body, disconnected from the coil. Should also be leak-proof, on a 'megga' or other insulation tester, to at least a Giga ohm at 250v if such a weapon is available.

Easiest cheapest thing is to fit a new condenser, then heat the mag up to about 50°C using a heat gun, low oven, whatever, and run it to see if it's any good. If it makes quarter-inch sparks at, say, 150-170-ish rpm, hot, the coil's probably good. You can - of course - just 'run the bike' if the mag isn't off it, to see.
If the problem hasn't gone away with a new condenser, and if the other bits, points etc, are good, then the problem comes back to the coil.