Next step in diagnostics?

[MarkO]

...but chaps - although the dynamo/reg may have the capacity to charge, the battery may be so weak and knackered so as not to take it.

[Chris Sealy]

With only 3.3 volts at its terminals, your battery probably has an internal short circuit in one of its three cells.
If that is the case, there is no way that it can charge to 6 volts. I would say that you need a new battery anyway.
You could try disconnecting the wire from the live terminal of the battery, insulate it to prevent accidental short circuit to the frame. Then start the engine. Rev it to about 1500 rpm, then switch the lights on and see if anything happens. Cheers, Chris.

[nevhunter]

You may have to "Flash" the generator to restore some residual magnetism to have it produce Power. You will need a 6v battery to do that. The battery may be "sulphated' if it's been left flat for a while. Sometimes that can be recovered. Digital chargers can do that. or try another 6V battery hooked up in Parallel. Discontinue if any cell gets hot. Nev

[nevhunter]

Lead acid Batteries last longer if they are kept charged. Vibration gives them a hard time Nev

[mattlacey]

You could try disconnecting the wire from the live terminal of the battery, insulate it to prevent accidental short circuit to the frame. Then start the engine. Rev it to about 1500 rpm, then switch the lights on and see if anything happens. Cheers, Chris.

I just tried this, and got nothing - going to order a digital regulator now pay day has arrived to see if that makes any difference, after that I'll get a battery.

[MarkO]

Do it the other way about perhaps.....

[mattlacey]

Got it! Turned out it was the regulator. Got hold of an analogue multimeter to test the dynamo properly and verified it was good. It motored, and it had output on the bike. So then hooked up the electronic regulator I bought and straight away the ammeter showed positive and the lights looked great. Orederd the one I linked to and it fits well inside the recess of the original unit.

[Julian Murphy]

Well done.

A good result.

[nevhunter]

You might have to cool that NEW regulator. Nev

[mattlacey]

It's designed to fit in there, so hopefully it'll be good. Will keep an eye on it though