Starter Motor - Positive to Negative Ground

Cheesehead Commando · Sep 28, 2024

After completing the rebuild of my MKIII and converting it to a negative ground wiring harness, I ended up purchasing a new Dyno Dave starter motor to complete the upgraded starter components that I had previously bought for the bike. Unfortunately I bought the starter motor meant for the stock positive ground wiring harness, forgetting that it won’t work with the negative ground harness I now have.

Before I begin the process of calling for what I hope is a refund and sourcing a starter motor with a negative ground, does anyone know if it’s possible to convert one of these without too much difficulty?
CNW used to stock negative ground starters, but no longer have any available, thus my dilemma as I had purchased the negative ground harness from there.

Thanks for your comments!

cliffa · Sep 28, 2024

Cheesehead Commando said:
After completing the rebuild of my MKIII and converting it to a negative ground wiring harness, I ended up purchasing a new Dyno Dave starter motor to complete the upgraded starter components that I had previously bought for the bike. Unfortunately I bought the starter motor meant for the stock positive ground wiring harness, forgetting that it won’t work with the negative ground harness I now have.

Before I begin the process of calling for what I hope is a refund and sourcing a starter motor with a negative ground, does anyone know if it’s possible to convert one of these without too much difficulty?
CNW used to stock negative ground starters, but no longer have any available, thus my dilemma as I had purchased the negative ground harness from there.

Thanks for your comments!

Have you contacted Dyno Dave? Perhaps he has -ve ground starters available or can advise how to convert it. I know it’s possible with the Alton, so should be with Dave’s.

gforce · Sep 28, 2024

Maybe I’m being a luddite.

Your starter needs to spin clockwise no matter how it is wired.

Surely in an electric motor with field coils (not permanent magnets like the Alton) it doesn’t matter whether it is positive or negative ground?

dobba99 · Sep 28, 2024

gforce said:
Maybe I’m being a luddite.

Your starter needs to spin clockwise no matter how it is wired.

Surely in an electric motor with field coils (not permanent magnets like the Alton) it doesn’t matter whether it is positive or negative ground?

You are correct, our starters with field coils will turn the same way with either positive or negative feed, the brushes need moving in the starter itself to reverse the rotation. Mk3 CNW starters are based on (or converted from) 5780BN prestolite replacement starters for Harley Davidsons . The Harley starter turns the wrong way, so when fitted to Mk3s the brushes are moved 90 degrees to reverse the rotation suitable for the Mk3. I would expect the Dyno dave starter to be similar. Connect the DD starter and try it, if it turns clockwise your go to go.

Cheesehead Commando · Sep 29, 2024

gforce said:
Maybe I’m being a luddite.

Your starter needs to spin clockwise no matter how it is wired.

Surely in an electric motor with field coils (not permanent magnets like the Alton) it doesn’t matter whether it is positive or negative ground?

Thanks gforce, I did test it with a battery on the bench both ways with negative and positive ground, and the starter motor did turn the same direction, which was clockwise when looking at it. So assuming it should be good to go…?

Starter Motor - Positive to Negative Ground

Cheesehead Commando

cliffa

gforce

dobba99

Cheesehead Commando

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