G12 650 CSR Alternator

[Stephenwalls]

Hi,

I have just replaced the magneto on my 1967 G12 with a Pazon ignition system. I have also re-wired the bike and fitted a new 3 phase regulator. Brillient! starts first kick every time!

Unfortunately, the alternator does not seem up to the task, as the battery is quickly discharged if I run the lights as well.

Three questions you knowledgable experts could help me with:

1) what is the model and output of the 12V alternator fitted to the 1967 G12 CSR
2)Is the alternator 3 phase or 2 phase (It's a 3 wire connection, but it looks like all the coils are effectively in parallel)
3) would fitting a Sparx high outpit alternator be reccomended? any one have experience of using these?

Many thanks for your help

Steve

[Groily]

Sounds as if the Pazon works a treat, as it should, but only thanks to a decent battery . . .

It's really hard to know what you've got on there Steve from what you've said so far. I'm absolutely not an expert but I'm sure originally it would not have had a 3 phase alternator. By 1967 it might have originally had (probably did have, but it's a bit new for me and someone else will confirm) a 2 wire single phase one, plus rectifier and zener diode. That arrangement would have been typical for the year, assuming the factory was right up-to-date! But it might have been modified subsequently in favour of a modern solid state rectifier/regulator combined (Podtronics or equivalent). Or, it could have had a 3 phase alternator put on. They give a slightly higher output at low rpm, but cost a lot relatively and not many people have bothered. If it does indeed have a 3 phase job, it needs the 3 phase regulator/rectifier you've got. If it has a single phase one, it doesn't. It would need the appropriately-rated single-phase equivalent. If it has the three-phase job and all is well, it should cope easily enough I'd have thought.

On the other hand it could have a single phase alternator with 3 wire stator on it, from a slightly earlier generation, whose coils would need to be switched in and out from the light switch because there was no regulator, just a rectifier and battery. On them, one pair of the leads from the alternator could be spliced and fed through to the rectifier + zener (or solid state single phase regulator) to make it work like a 2 wire one by delivering full output all the time. But maximum power was limited to around 90 Watts. Probably not enough to handle a 60/55W light, ignition, sundry other bulbs - and charge the battery. Lots of possibilities, sorry, but who knows what's where after 43 years . . .?
You need to establish for certain what bits you've got.
If you look at Paul Goff's site, you'll see - and he knows - that he recommends the 190W single-phase alternator plus appropriate regulator for those of us who want to run Pazon, Boyer etc as well as being able to see in the dark!
Personally I run a 2 wire 120W single-phase alternator on one bike with standard coil/cb ignition, and a 190W single-phase job on another with brighter lights and a Boyer system. Both have solid state regulators, and both work fine under all normal loads.
I'd try to establish first whether you really have a 3 phase alternator on there, because if you haven't, that's your first issue. Don't know about Sparx thingies, sorry. I'd have kept the mag - but that's another subject altogether!
Good luck!

[wilko]

I've read on occasion that the Sparx versions rotor can be slighly undersized for the crankshaft, and that the stators might need a skim to fit the outer case, can anyone confirm?

[Don Madden]

A while back I fitted a stator to a 1966 G80CS & had to skim the outside to fit the cover. I don't know who made it but it came from DomiRacer. Cheers, Don.

[Stephenwalls]

Thankss for the replys!

I've checked and whilst the alternator has three wires, it's only two phase as Groily suspected. The Pazon ignition is taking about 2.5A, so a 5A 12v alernator is always going to struggle when the lights are on, as this inreases the total load to 7.5A!

The pazon ignition works so well, I can't take it off. I think I'll take a look at Paul Goff's site, or buy a Sparx system. It's either that or ride a lot faster in a lower gear!

Has anyone else tried Paul Goff's alternators with a similar set up?

[wilko]

If it has a 3 wire it still potentially has around 100 watts just by joining 2 of the wires together! A common conversion i've done plenty of times.

[Groily]

It may be, Steve, that the stator you've got isn't wired in properly at the switch to permit the full output (via that third wire) when all loads are on. Even the smaller Lucas alternators should be capable of giving 90 watts + at decent rpm as Wilko says, which is your 7.5A, although it would be marginal. Definitely worth a look at Goffy's site to see how to wire a three-wire stator for constant full output with a proper regulator - your colour-coding may even match what he describes, you never know! (You need to go to "Motorcycle Electrics" and then click on "12v alternator wiring diagram and details on converting 6v to 12v" on his site.)

However, you might be better off, while you've got things apart this far, swapping out the stator for a bigger 2-wire one and simplifying the wiring at the same time. Certainly, that would be his recommendation with your Pazon system.
My 190W stator easily supports a Boyer ignition system and a 60/55 halogen light (that's on an Enfield twin), using one of the higher-rated solid state regulator/rectifier units. Famous last words . . . but I hope not!

[Stephenwalls]

Groily, thanks again for your help. As I mentioned, I've already completely rewired the G12 making the selector switch redundent and added an electronic regulator so the . In the process I have already connected all the coils for maximum output (thanks Wilko). I'm encouraged by the fact that Groily's 190W gives no trouble, especially as, after a little modification, I've managed to fit a 5 AH battery. Groily, did you buy your 190W alternator from Paul Goff? If so I think I will go that route.

Many thanks for everyones help

[Groily]

Sorry Steve, hadn't picked up you'd already sorted the three wire thing . . .
In this case I didn't buy a new stator as the 190W job was already on the machine when I bought it. I suspect the PO got if from Paul though. It was hooked up to a Boyer PowerBox initially (alongside the ignition unit), but that died, and I bought the higher-rated single-phase reg/rect from Paul, which has been fine so far. It's not a bike I ride too often as it's a café-racer and kills my ageing back, so I have a battery isolator on there. The Boyer basic (Norton-type) ignition unit needs about 9v minimum to trigger it, and so far no problems even if I leave it for a few weeks.
Re the battery, I tend to go for the largest thing that will fit the space in terms of A-hours - that's the pessimist in me wanting to get home regardless of what might go wrong on any bike without a magneto! Plus fingers crossed the battery will maintain enough charge between days out.

[Malleon]

I bought a Wassel encapsulated stator from Goffy, 12-volt single phase, 120 watts, but am having difficulty fitting it to the outer chaincase of my G3.
It is a very tight fit, and I have been advised not to machine the stator to fit. Please, Don, could I have the chaincase machined instead? I also bought a slightly larger rotor with excellent magnetics, also a tight fit!
Help!!
Best regards