Hi, hope someone can help. I have an old Brit bike with a positive earth system. I want to put a regulator on it and have one off a CZ, which is a negative earth bike. Just wondered if I could use it on my positive earth bike! As you can see I know nothing about electrics. Oh yes I have a rectifier which also, which would be first in the line and can be wired for either a positive or negative earth, Cheers.
bwg11,
Aug 2, 8:40am
Only guessing as you have had no replies. With old Lucas regulators polarity was irrelevant from the regulators viewpoint. I just swapped from positive earth to negative on my boat tractor to be compatible with LED lights on a new trailer. If the british bike has a generator (or magdyno) and not a flywheel alternator I don't think a rectifier would be needed.
budgel,
Aug 2, 8:45am
I am assuming you mean an old fashioned non solid state regulator.
It would work but you would need to keep the body of the regulator separate from the frame of the bike which will be positive, and hardwire it to the negative circuit.
My brit bikes used a zener diode for the regulator, (they were 12v though.)
andrew1954,
Aug 3, 6:04pm
Keeping the body of the regulator "electrically isolated" from the motor bike frame should get around the neg / positive earth problem BUT the regulator may be designed to operate with the metal body of the regulator in direct contact with the frame to act as a heat sink. you may have to consider this
sr2,
Aug 3, 6:15pm
Never changed the polarity of a bike but when we used to change the polarity of generator charged cars all we had to do was re-polarize the generator by momentarily jumping a +ve wire to the field terminal. The regulator was not polarity dependant and required no modification or isolation.
sparkyz,
Aug 3, 6:32pm
The Lucas RB108 is not polarity sensitive. Just do what sr2 said to polarize the generator.
glyn4,
Aug 4, 10:09am
Thanks for all that great information. I believe these 6V PAL regulators were used on tractors in the day and yes the unit is bolted straight to the frame. There is a big resistor looking thing at the base of it, which has a tang off it, which goes straight to the case, and therefore to negative earth on the bike. I suppose the only really way to tell is to wire it up and give it a go. Cheers all.
Since the public registrations are closed, you must have an invite from a current member to be able to register and post in this thread.
Have an account? Login here.