With the original wiring, the voltage was controlled, not very well, by the lighting switch. When the lights were off, only one pair of coils on the alternator were connected, to charge the battery. The other coils were used when the headlight was on. This is why single phase alternators form that era had 3 wires and not two. Lucas also reduced the power output of the alternators around 1960. But for most people, the battery was overcharged, depending on your riding style. PAZON RR12-6 voltage regulator would work and give you the option of 6V or 12V. May be available form the Bonneville shop (I have not checked), and there may be other manufacturers with similar products.

Hi Rob! The early alternator Triumph 650s didn’t use a regulator. The 6 volt alternators were prone to overcharging as such, so it was recommended to run with your headlamp on all of the time, as the current draw from the lighting system would help consume any excess current generated by the unregulated charging system. The wiring diagram reveals how the wires from the rectifier are connected directly to the lighting switch, through to the ammeter to the battery. The lights act as the regulator in this system. Those big rectifiers are robust instruments and many have survived over the years. I understand you would prefer to keep the 6 volt system. If it charges to around 8 volts and doesn’t cook batteries, I would keep it original. The 6 volt regulators I have seen are designed for use with DC generators, which required a voltage regulator, but not a rectifier, as the voltage supplied was DC, rather than AC, as from an alternator. The Zener diode debuted in 1966, when the charging system changed to 12 volts. If you don’t want to convert it to a 12 volt system, I would leave it all stock. Feel free to give us a call too!

I’m sure there is a scientific procedure to remotely measure the magnetism in a rotor, but it is not mentioned in the Lucas Service Manual or the BSA and Triumph Factory Workshop Manuals. In practice, if you can pick up the rotor by applying a long screwdriver to one of the magnets, and wave the screwdriver around, and the rotor sticks to the screwdriver, it has sufficient magnetism. If it falls off of the screwdriver with very little, or no movement, it is questionable and should be renewed. Another thing to inspect is the steel center insert. If you can place the rotor on the crankshaft, with the key fitted, you can check to see if the center boss is secure in the body of the rotor. If there is any looseness of the center boss, the rotor will require replacement. If you see stake marks around the center boss in the rotor body, somebody has already discovered looseness. Hope this helps.

When i got the rotor off it was moving on the steel insert no good wouldve affected ign timing and possibly spun so i pissed it off and fitted a new 1 i went with a wassell solid state rectifier and a 10 amp single phase stator .... now the rings are shot lol its all fun and games but hey we learn