How many years does a new magneto coil keep its magnetic charge? On average.
Then why have mine lost their magnetic charge and I see videos of magneto coils being recharged?
Is there preventive measures?
It is not the coils which are recharged. It is the magnets which move by the coils when the crankshaft turns.
One reason for the magnets discharging is if someone connects the battery to the magneto post. This is sometimes done by accident and other times when the wires just happen to touch each other as in a switch problem or or wires too close at the terminal block.
The coils do not hold any magnetism, the magnets work upon them to generate an electric current. The coils should remain serviceable for an indefinite time unless damaged by things like the starter bendix. The magnets, on the other hand do gradually loose their magnetic field as it naturally degrades. You can do things to speed up this process such as touching another electrical source to the mag post in any position other than the correct charging configuration.
I see that Norm is faster at typing than l.
Magnets do lose some of their charge over time, but if they aren't accidentally weakened as Norm described it takes decades. After ninety years a lot of cars will no longer start on magneto, but have enough charge left to run on MAG once they're started. Most still run better on MAG than on BAT, even if they will no longer start that way.
My unrestored '17 runs fine on magneto.
My 17 has never been recharged since new. It easily starts with the crank on Mag.
Thank you for the information.