6V positive earth Wassell reguator mystery

[PeteB31]

I have recently purchased a B31 at auction and whilst the bike appears to have been restored to a good standard 20 years ago or so, the electrics have me completely baffled. The attached picture shows a Wassell regulator mounted just ahead of the battery. The green and yellow wires go down to the dynamo. The red wire joins a positive wire from the battery and is earthed to the frame on the right hand side. The black wire goes left and and is earthed on the left hand side, an attached wire goes down to the earthing point on the magneto body.
This can't be right, can it? Can anybody throw any light on this?

Thanks.
Pete

[iansoady]

No, agree it isn't right. I'm not familiar with the Wassell unit but in general the red wire would be positive and black negative (as you have). However, I'd expect the bike to be positive earth so the red wire to earth would be correct but the black one should go, via the ammeter, to the negative battery terminal.

Is the battery charged? I'd expect the setup you have to create a dead short.

[PeteB31]

The bike is positive earth. The battery is charged, although that could have been done by an external battery charger. The ammeter in the headlight shell has no wires attached. The feed from the battery goes to terminal no 2 (headlamp terminal), so no horn or lights until the headlamp is turned on.

[BUNNERS]

A quick look on web for Wassel 6v reg diagram gives the following
YELLOW to D- on dynamo
GREEN to F field coil
RED to E field coil
BLACK to fuse and Neg - on Battery
Battery Pos + to chassis earth

[PeteB31]

Yes, absolutely nothing like how mine is wired. My concerns are, as mentioned by iansoady, this would seem to be a dead short. So will the regulator be fried, even more important will the dynamo be damaged.
I'm way out of my depth, hence throwing it out there for guidance.

[iansoady]

It's quite hard to seriously damage dynamos.....

From what Bunners says, the red should be to earth / battery positive as this is the same as conecting to the earth end of the field on the dynamo. I would suspect the regulator is defunct. Wassell don't (and never) have a great reputation but I've used some of their stuff successfully. I think it's more a matter of quality control than fundamentally poor quality - these regulators are quite simple beasts.

[cdsdorset2]

Have you removed the unit to see if it is +ive or-ive unit. Its normally printed on the back. Just guessing until you check that.

[PeteB31]

Yes, 6v Positive printed on the side.

[V500]

This bike sounds like a prime candidate for a complete rewire, possibly with a new (DVR2) reg too.

[PeteB31]

That's a sound plan. Am making up a shopping list now of goodies required.

[cdsdorset2]

I always use AO regs. You can order them direct from Alan who is very knowledgeable

[V500]

While I wouldn't ever use them again, mainly down to their 2A discharge at tickover and a low charge rate under 30mph, and their strange habit of not "switching on" sometimes.
The seller is a miserable sod too. DVR2 everytime for me.

[cdsdorset2]

Ive never had a problem and fitted a fair few.
Alan is an aquired taste and you need to get to understand him. He has talked me through many wiring questions and has given me great service when i need to buy anything.

[PeteB31]

Thank you all for your comments.
A complete re-wire seems to be the first stage. Not holding out much hope of the current regulator working, but will give it a shot first before ordering a replacement.

Pete