Negative Earth and Starter Motor

Hello, I am starting to rewire my Mk3.

It has a Pazon system with a Pazon Regulator.

I would like to wire it Negative Earth,

All is straight forward except for the starter motor, which I believe will spin the opposite way if it's wired negative earth?
Is this right? If so how can the bike be wired negative earth and retain the starter?

Also what it the black box 06-6393 "control unit, warning light" is it needed? What does it do?

Regards Graeme.

GRM 450 said:

All is straight forward except for the starter motor, which I believe will spin the opposite way if it's wired negative earth?
Is this right? If so how can the bike be wired negative earth and retain the starter?

Click to expand...

No, the starter will spin the same way if it's connected negative earth/ground.

GRM 450 said:

Also what it the black box 06-6393 "control unit, warning light" is it needed? What does it do?

Click to expand...

The box switches off the red charge warning lamp above idle speed if it senses there is output fron the alternator (except Canadian model 06-6392 boxes that also switch the headlamp on once the engine starts) so you don't actually need it, but you won't know if the alternator is working or not.

Thank you L.A.B, I thought that as the starter is a DC motor that if the polarity was reversed the motor would spin the opposite way.
That make the wiring very easy.
I'll check the wiring diagram thoroughly so I can use the control box.

Thanks again,
Regards Graeme.

GRM 450 said:

I thought that as the starter is a DC motor that if the polarity was reversed the motor would spin the opposite way.

Click to expand...

As the motor's polarity is reversed in both the field coils and the armature, the motor continues to rotate in the same direction.

Graeme,

Les provided an assimillator circuit diagram in a recent post that makes it clear that it is hopelessly positive ground (it contains diodes and a p-n-p transistor, if memory serves). Negative ground assimillators are available from Old Brits, if you want to keep the function alive. You may want to test the solenoid for reverse polarization, as the input is referenced to case ground. The inputs are often diode protected, and won't like a reverse voltage. Exciting the solenoid from the positive tab wrt case, as opposed to the negative tab, may work. If you find that this works, could you report back? I'm looking for a winter project for my Mk3, and negative ground would be ideal.

Rick

Hello Rick,

I had an old solenoid that had a cracked case. I pulled it apart and there is no diode inside. Just the coil winding.
So there should be no reason the polarity can't be changed as for as the solenoid is concerned.

Keep in mind this is all 1977 Mk3 stuff. I do not know what the earlier models have.

I'm having doubts whether it warrants changing to negative earth as I haven't heard a good reason to do so.
(as yet)

Regards Graeme.