john deere m

cb42 · Jan 17, 2015

what all needs o be changed to convert from 6 v to 12 v ?

pmsmechanic · Jan 17, 2015

I've never done the job but from what I understand the starter and the wiring will be ok with the higher voltage. So all you need to do is change the bulbs, adapt an alternator and change the coil. Most alternators are negative ground so you will need to change the battery connections as I believe the M is positive ground. Also the connections on the coil. On a positive ground system the points need to be hooked up to the negative terminal of the coil. You might need to replace the resistor for the coil but I'm not sure on that. If you buy a coil for a ~ 60's Chevy with an internal resistor then you can just wire the + side of the coil direct to 12 volts.

beenthere · Jan 17, 2015

Some google searching will turn up several hits to support what pmsmechanic suggests.

one hit
Yesterday's Tractors - Converting from 6 Volt to 12 Volt

Was always thinking about doing this with my 2cyl 420, but didn't need to after I had the engine overhauled and it fired easily with the 6v system.
Wish I'd kept that old 420 but didn't have shed room and couldn't bear to let it stay outside in the weather.

Soundguy · Jan 17, 2015

Not familiar with an m as to if it had a coil or magneto.

If coil, get a Napa ic14sb, if magneto, Nada to do.

Alternately, you could get a proper ballast resistor and retain the old coil, but I'd get the new coil.

As said, change lamps.

Likely you will be changing ground polarity if you are going to an salt or an electronic ignition.

For stealth conversions you might be able to get your gen rebuilt as 12v, and get a new regulator or cutout. If it uses a lamp tickle switch, you could retain that or not, if you keep a Genny and convert it..e tc