Ariel Owners Motorcycle Club

Early JG dynamo control units required the field coil to be wired not to earth but to
the 'D' terminal, as described above.

Somewhere in the collection of parts you may just find an alloy box about 5" long
by 1" wide and 1" high with three wires coming out. I've had one on my Mk1
since the JG units first came out. It suffers the usual problem of needing more revs
to get 12v but otherwise it has been fine.

Just a thought Brian. Did you get a dynamo control unit with the bike?
If so, what make is it?
I'm wondering if you have a non Lucas type of control unit.
The Lucas system controls the output by varying the current flow between terminal D and F.
There is an alternative system which controls the output by varying the current flow between F and ground.
It may be that your dynamos internal wiring has been modified to use one of those.

Delighted to report that problem solved! The schematic supplied by Simon instantly solved a week of frustration. The previous owner had connected the tail wire of the 2 coils to the D terminal. The drawing shows it should go to ground. Switched the connection and everything worked as it should, linked F/D and it motored, spun it at 1000 rpm in the lathe and it was producing 7 volts. Now I can get on to finish rebuilding the engine. One last question, ( until the next crisis ) any recommendations for an electronic voltage regulator for this generator?
Many thanks to all, just goes to show the power of the club!

I'm delighted to be of help Brian. I've had an AO Services V-Reg 2 connected to my CS35D for the last 12 years or so. I use them in all my bikes now.

The AO available from Drags is the only one rated rated high enough for the C35SD (that I know of)