[Spider_Webb]

Hi, bike is originally a 1982 350 Bullet (refurbed and imported from Delhi) With a 500 5 speed left gear change engine/box.
I am getting 12.3v DC at battery when running. Alternator is 4 wire producing 55v AC at black wire, 18v AC at yellow wire. 8v AC at red wire and 0v at orange wire all measurements at 2 to 3 thousand rpm. Could anyone tell me what are normal output voltages? Thanks.

[Spider_Webb]

Also it has a 4 wire regulator/rectifier, 25v AC is present at input to this. Should this value be slightly higher?

[stinkwheel]

I'm guessing with it being it refurbed bike, it doesn't have a 1982 electrical system. Is it an AC/DC setup or all DC (if AC/DC the headlight would only work when the engine is running).

It looks like the standard AC/DC system they use on later model bullets from your pictures. If that's the case, the black and red going to the two violet wires go to the reg/rec and charge the battery. The yellow and orange power the headlight.

If I was measuring AC output, I'd be measuring AC volts between the black and red and I'd measure it between the yellow and orange with the wires disconnected rather than between each wire and earth. probably in the 20-50v range depending on revs.

12.3 at the battery is probably right at idle but I'd expect it to go to somewhere between 13 and 15v (no higher) with revs.

If it has the standard 2-piece reg/rec, they are terrible and are usually responsible for charging problems. Use amost anything else instead. So if your AC output is roughly where you'd expect it to be, suspect that reg/rec. Recently, I've been using a sparx single phase reg/rec with an internal capacitor which works great and has the benefit of self-exciting so it'll run with a flat or no battery. If you want a budget alternative, the lucas single phase 12v ones are entirely adequate. https://www.feked.com/12v-lucas-regulator-rectifier-single-phase-solid-state.html Or you can re-purpose a used japanese 5-wire one, just miss out one of the charging phases, I've had a ZX6R one on my 350 bullet for over 10 years now.

A dead/dying battery could also simply not be taking a charge so worth charging it and seeing if it's holding a good resting voltage, I'd expect around a 12.3V resting voltage and it to be the same when re-checked after sitting for a day or two.

Also check the frame earth connection from the battery negative. Usually a ring terminal on the bolt holding the battery box on. These are often corroded or simply bolted on over the paint, make sure it has clean metal to metal contact with the frame. Get busy with some emery paper then cover it with dielectric grease/vaseline once bolted up.

[Spider_Webb]

Hi, thanks very much for your detailed reply. The bike seems very well refurbished and all electric parts and looms etc. are new. DC volts at battery are max 12.5 at high revs. Battery is very good, holds charge for weeks and cranks engine well, I can charge it up at night and use it all day with electric start with no problems. I have just checked the earth wire and it has a good clean connection to the frame. I get 0.3 ohms between battery neg and frame and 0.6 to engine. Black and red get max 70v ac and yellow and orange get mav 50v. For some reason the violet with black stripe is not connected at all but other violet is. I tried joining them but still get 25v AC presented to reg/rect. I have just tried a new reg/rect and still only get 12.5v DC at battery at high revs. Headlight works with engine only.

[AzCal Retred]

If the battery is cranking well and holds a charge for a few days, I'd double check the meter DC scaling. Trust but verify. Check against another meter. Should be close, +/- 2% or so.

The measured AC RMS voltage coming into the reg/rec is double the DC output. Both reg/recs have made the same output by your DC scale. The battery is holding a charge and cranks well. As Stinkwheel says, AC varies with RPM.

A bad battery cell would put you at 10V overnight or worse. Both reg/recs would have to be failed in the exact same manner. If it's working well, I'd look at the meter.

[Spider_Webb]

Hi. Battery is fine, I can charge it overnight and use it all day with electric start. Headlight is not via battery. I have checked the frame earth, all good. I am getting max 75v AC across black and red and 50v AC across orange and yellow. I just fitted a new reg/rec unit and still get 12.5v DC at battery on approx 3000 rpm. Violet with black stripe not connected to anything, tried joining violets but still only getting 25v AC between reg/rec feed and earth.

[Paul W]

My Indian home market 350 Bullet Electra gives 14.5v when running. From what you’ve said,  I’d check yours using a different voltage meter!

[stinkwheel]

Next question is, do you actually have a charging problem? Is your battery going flat?

If your battery is still resting at 12.3V and able to crank the engine over on an electric start after a days riding, is the "problem" real or simply theoretical?

[Spider_Webb]

Thank you for your replies. The volt meter is fine. My other meter reads exactly the same. The battery is clearly not charging or I would not have reached out here for advice.
I have decided to buy a Lucas alternator and when I get round to fitting it I will post my results here. Thanks again for all suggestions.

[AzCal Retred]

Get all of the Lucas bits, alternator stator, rotor & reg/rec. That way they'll be likely to play nice together, less guesswork. The 150 watt item is always a good choice.

[axman88]

The AC voltages sound quite healthy, but does the stator deliver power?  Is the orange/yellow coil lighting the headlamp?  What happens when you assign the charging coil (black / red) to the headlight power circuit instead of using orange yellow?   This should be safe for a short test although I would think it would overheat the AC regulator in extended service.  If I had one, I'd hook a 2nd headlamp in parallel to give the charging coil a bigger load.  If both coils are capable of lighting the headlamp (or headlamps), I'd personally call them good and move along.

It sounds to me like there is a discontinuity between the AC and DC sides of the charging system, something that could be present either inside the Rect/Reg or external to it.  Can we assume that you have verified that the wiring for the charging circuit is continuous, and the connectors are making connection?  I'd do this by probing the furthest points of each conductor, and verifying continuity.  One can "back-probe" connectors, or stick a pin through insulation on a wire to further along a conductor if there is some evidence of discontinuity.

Getting further "Out there", although I've never seen the fault, and never heard anyone else describe finding it in practice, I have the idea in my head that a regulator could be fooled into regulating to a lower value at the battery by being attached to a high resistance conductor, on either the the power side, or the ground side.  If some IR voltage drop is occurring in one or both conductors between the battery and the regulator, it seems to me that that the regulator could be doing its job just fine, completely ignorant that the battery was seeing a substantially lower voltage.  Ohming the conductors, voltage drop tests, or the use of known good bypass jumpers from battery to regulator could quickly rule this possibility out.

[Super45]

Cheap stuff first...

I'd start by testing to see if the bike produces any power at the reg/rec connectors.

if it does the reg/rec is faulty, not unknown for new Indian branded ones to be at fault as Stinkwheel has said, I should know I bought 3 genuine ones which were broken from the factory before I gave up and went to Rex's speed shop for  plug and play single unit one

https://www.rexs-speedshop.com/shop/?s=royal+enfield+

just pick which one you need, bullet connectors or one large connector.

 if no power at connectors work backwards from the reg/rec to the alternator till you find the issue.