Battery or earthing problem?

[Hubie]

I connected the earth terminal to both the body of the dyno and then on the side stand mount on the frame.  Both times it motored.  I too am at my wits end!  I may have to bite the bullet and send it to COD rewinds.

[MG]

Didn't you have it refurbished recently? I would contact whoever did this first and have him fix it.

[a101960]

Just because a dynamo will motor that does not mean that it will generate. Motoring is not a reliable indicator of a dynamos serviceability status. A dynamo will often motor even if one or two armature segments are U/S, and the reason for this is inertia. Once the dynamo is motoring then the motor action is maintained due to inertia generated by the armature as it spins. This can give a false impression that everything is O.K. Motoring a dynamo can indeed be used as a diagnostic aid, but it is far from being a reliable method of serviceability assessment. Really all motoring a dynamo can prove is that it motors.

[MG]

Yep, I think we have excluded all other possible causes, looks like the dynamo is faulty.

[groily]

Going back about 4 pages and half a lifetime, what did the man actually do to the dynamo Hubie?

With the brushes - as you confirm - wired one to D, the other to E (they absolutely have to be that way), and one field coil connection from the same E (per Brian's pic) and the other to the F terminal, then it's wired right on the inside. If the polarity is indeed set correct, and proven if it motors the right way when driven off a battery with the neg to the F and D bridge and body/frame/earth return to Batt +, then the thing's hooked up correctly. There's also residual magnetism in there, and the brushes are doing their job.
3 additional thoughts.
Can't remember what regulator you're running. If you have an electronic JG unit that requires the field to be wired F to D because the regulation is done on the live side not the earth, then it won't work. But nor should it motor hooked up as described, as you'd have to bridge F to the body/earth, connect the body/earth to Batt +, and D to Batt live. So that's unlikely.
On A101960's motoring and inertia point you might want to run a simple test on the armature, as it does appear it may be suspect. Suggest you measure the resistance across every commutator segment to every other one. There should be a similar, low, resistance across each and every pair. If there are pairs where the resistance is very high or infinite even, then there are winding faults on the armature and further investigation is needed. But this would be BAD if you just spent money having the thing looked at.
And lastly, if all else fails, are you sure the field coil and armature are compatible? If the man changed either, did he put in  'standard-wound' equivalents to the Lucas originals? If he put in a '12v' field coil (there are lots of them about) it will take a lot of revs to make the standard armature generate anything much you'd notice although it may/would still motor. An original field coil should show about 2.7 to 3 ohms across its ends (and no reading from either end to earth); a '12v' one designed to work in conjunction with a finer-wound modern replacement armature should show about 11 ohms. (Another highly unlikely scenario, but we seem to be moving into the realms of head-scratching from the normal comfort zone where things do what they are meant to do.)
Hope you get to the bottom of it . . .

[muskrat]

G'day all,
                been watching this with interest. Something strange happening in the dynamo.
Dave, it looks like a trip to the auto sparky. Down here it's getting hard to find a sparky that is really up on dynamo's.
Only 1 out of 3 in my local area will touch them and he's retired, but luckily he has a Goldie,RGS in bits,Thunderduck and a Vauxhaul 6. He did mine for a slab.(beer)
Cheers
PS just saw groily's post. I know the HD gennie is different to the Lucas. Maybe the sparky wired it like one of them. Just another straw.

[Hubie]

I'm dropping the dyno off in seaford this morning to see if we can sort it out. I only have a digital multimeter and I am getting fluctuating readings on the field coil resistance so maybe the field coil is stuffed.

Will keep all posted.

Dave.

[trevinoz]

Dave,
              All I can say at this point is I wish I had that **##* generator on my bench.
I would soon show it who's boss!
             Trev.

[Hubie]

You never know mate, if my friends down in seaford can't fix it I might even send it up to you!

[bsa-bill]

I might even send it up to you!

Interesting quote for us Poms, which way is up down under   
Flame suit on    bags packed

[groily]

Well, me mum always said North had to be up . . . and so South was down. But Poms always used to go 'up' to London even when they were going down . . . so I dunno! No-one apparently ever went left or right though - which is maybe why routes are always so much worse in some countries going across . . . weird but true.

[muskrat]

I can't go right ! Next stop NZ !
Cheers

[groily]

And I can't go up, either - without water wings and a passport . . .

[Hubie]

Dyno is apparently ready to go.  I was told that the brushes were very worn and had a diagonal chanel across them causing them to come into contact with more than one commutator segment at a time.  Will be interesting to see how it goes when I get the chance to go pick it up.  Shall keep all posted.

[Hubie]

I think we're near the end.  I have put the dyno back on the bike, pumping out very healthy voltage.  I have the vreg II on the bike and when revved, it pumps out good voltage also.  Thing is, i have no lights and the ammeter doesn't move even though there is power to it after checking with the multimeter.  Do I have a stuffed battery?

It was under 6 volts, about 4.8.  At this voltage the dyno only puts out 1.2 volts at revs.  I am thinking along the lines of battery as I have the electronic type reg and from reading back through these posts it seems as though it needs decent voltage from the battery to start running.  Any thoughts?

Dave.