6 volt or 12 volt

[groily]

and if you can revive your 6v dynamo that can still charge a 12v system

Especially with a belt drive conversion to gear it up a bit. Ran my A so equipped for14 years and a load of miles in almost daily use with a halogen lamp, but would probably go for one of the better LEDs nowadays, such as the ones from Dynamo Regulator Conversions. Their 'Ultimate' LED (for H4 fitments) is extremely powerful, but expensive, their PRO versions less pricey but also pretty good. Have been using both, plus other LEDs from Paul Goff.
(If of interest to anyone, their converter rings to get from 'P43T' to 'P45T' is a very handy little gizmo indeed - I use them to enable use of a couple of Cibié concave headlamp units, which are to my mind the closest we ever got to modern-quality illuminations for night-time use on classics.)

[limeyrob]

12V does the same job with half the current so its more forgiving of old wiring but a dynamo comes up to charging at lower revs on 6V.  12V is also less sensitive to dirty connections due to the lower current flow so i solder as much as possible on a 6V set up.
My A10 is on 6V and LEDs plus a home made indicator set up that works well.  The 6V LED indicators need a 6V incandescent warning light in the circuit to trigger the flasher and buzzer.
My Matchless is on 12V with no dynamo, LEDs and a LiPo batters that gives a couple of hours lights as its set up as a lightweight trail bike.

[Bsareg]

My little C11 is still on 6v 40w dynamo. To enable a brighter headlamp I've fitted a bright 12v LED with a tiny 6v to 12v inverter in the headlamp shell that is only activated when the headlight is in use. Been in use for three years, no problems.

[fffcycles]

Done the same on a couple of my Bantams and one of the Ariel’s. Good conversion and cheap I think
Frank

[muskrat]

G'day Rickj 
As per a few replies 12v gets the nod with me as well. Belt driven dynamo and DVRII reg.
Cheers.
Now get over to Introductions and give us your story.

[Rickj]

Thank you for all the helpful replies. I've now decided to go with 12 volt. I knew the dynamo wasn't working when I bought the bike, stripped it and found no issues, 3ohms resistance on the field winding and it runs as a motor on 12 volts, so I think it's probably the regulator. So I just need to fork out for a dynamo belt drive and a DVR 2. The number one issue now is converting the front brake to TLS.

cheers

Rickj

[mikeb]

Rickj - yes dvr2 and belt drive/pully are good (get the one with the smaller dynamo pully / better ratio and the screw threads to pull it off - i think its the not srm one, can't recall who). and good the e3l runs as a motor etc. but you may need to run it for a couple of hundred miles before it 'wakes up' from a long sleep - i think remagnetizes is a more accurate term. maybe even do that first unless you already have the timing chest and wallet well open  - ok yes i guess do the dvr2 as you are up for battery and bulbs to 12v it - the belt drive could wait. keep the blub wattage down and consider LEDs.
there are lots of threads about a tls setup - worth doing in my view but not mission critical it you are first just getting the bike back on the road. a well setup sls is not completely terrible aND YOU GET TO RIDE THE BIKE!!!!

[Swarfcut]

 Cheapskate trick to get an old reluctant sleeper to give power is to apply battery voltage directly to the field coil  for a few moments as the dynamo spins. Initial output is determined by the residual magnetic field retained in the pole shoe, so on a neglected unit this will be marginal or non existent. Powering the field coil gives a good magnetic field, a little bit of help if you like.

 Once it starts to generate, this jumper can be disconnected, the regulator effectively doing the same job by applying pulses of voltage to the field coil, changing the field strength and thereby altering and controlling the output. Watching an old Lucas regulator working in the dark will reveal a series of small sparks as the regulator contacts open and close rapidly as they go about their work.

 Residual magnetism will build up with use, Mike's on the money here.

 Swarfy.

[limeyrob]

Yes, my dynamo was being woken from a very long (20 years) sleep and then swapped from pos to neg earth.  I motored it then bench ran it as a genny and it gradually got better at exciting.  On the bike it would not excite with the mechanical regulator so I got a DVR2.  The DVR is (as they claim) much better at exciting the dynamo. That said at the moment it needs one blip to about 2000 rpm on the engine to get it generating, but after that it generates from around 1000 rpm. I expecting (hoping..) it will come up to volts quicker with more use.

[a101960]

12v

[Worty]

6v for me, works fine and I like the originality of it.  If I need extra light in the dark, I stick a candle on the front mudguard and ride a little slower.

[trevinoz]

Rick,
It motors with 12V but does it motor with 6V?
A bad one will motor with 6V and a good one will motor as low as 3V.

[Rex]

Regarding residual magnetism, I seem to have to wake up (or the correct tech term, flash) the dynamos on my bikes every Spring. Just run a jumper wire from the non-earthed battery terminal and touch the F terminal on the dynamo  a couple of times.
Bike doesn't need to be running though it's safer to pull the dynamo connections out first.

[groily]

Ah. Maybe you need a 'nudger' Rex, along the lines we were talking about here a while back. Here's the thing again. (Might help Rob too with his lazy one on days when it's slow to excite.) Memory's fading but I think Trevinoz also suggested a switch & small bulb off ammeter and back to D as a nudger plus charge warning light  . . .

[Triton Thrasher]

Tell me if I’m remembering this stuff wrong.

I think the charge warning (“Ign.”) lamp on a dynamo-equipped car served the “nudging” purpose described above, by feeding a small current to D, which was connected to F when the regulator contacts were in the no-charge position.

You can fit a warning light to a bike with electromechanical control box, across A and D, but you need a battery isolating switch.