HONDA CG125 - Charging Issues?

[Kieranroberts...]

Hello, My Honda CG125 1996 is only outputting around 6v whilst idling.
(Tested Yellow cable to ground).

What tests with a multimeter can i do to diagnose the problem?
Faulty Stator? Regulator?

Should i get resistance from the wires (Yellow, White, Black+White) to earth or not?

What sort of readings am looking for?


(Lights do get a tiny bit brighter when engine running but not "12V bright")

Cheers
____________________
Cornwall

[stinkwheel]

How was the meter set? Should be volts AC to measure raw generator output (white to ground and yellow to ground). It'll fluctuate wildly. It wont generate much at idle, you'd normnally check output at middle to high revs on this type of charging system.

Where are you testing? There shouldn't be a black/white coming off the stator. Only the white and the yellow are concerned with generating power. The red on black is for the spark so if the engine is running, leave it alone.

You'd normally check charging output in volts DC across the battery terminals.

You'd check lighting output in volts AC between the yellow and earth with the light on. Or at the light itself.

It's still direct lighting so if the headlight is coming on, the generator is broadly speaking, working. Don't expect them to be like a modern bike, it's a 35w tungsten filament bulb powered by a single charging phase. It's there to be seen by, not to see with.
____________________
“Rule one: Always stick around for one more drink. That's when things happen. That's when you find out everything you want to know.”
I did the 2010 Round Britain Rally on my 350 Bullet. 89 landmarks, 3 months, 9,500 miles.

[Kieranroberts...]

Hello,

Sorry, i did not explain very well!.
Cables coming out of the flywheel, the black and white is for ignition and red and bluely/grey for neutral switch.
Which, as you said, leaves white and yellow for power.


I think played around with both AC and DC setting just to be sure, and never got anything close to 12V. I also tested the battery whilst running and i am sure it said -8.62V or something? again, i vaguely remember switching between AC/DC to be sure, nothing near 12V again.
(i tested it a couple days ago).


To be fair i don't think i actually tested the white cable to ground. I will try that.

I am an Electrician by trade so have a good understanding of circuits, wiring diagrams etc.

Sorry for being a newbie! Im trying to learn for future, this is my first bike that i bought as a running project.



EDIT:

Resistance Readings from Regulator Rectifier:
+White -Red 09.67 MegaOhms
+Green -Yellow 10.17 MegaOhms
+Yellow -Green 9.45 MegaOhms

Resistance Readings from Stator:
Continuity between Yellow and White = 000.5 Ohms
Continuity between Yellow and Ground = 000.6 Ohms
Continuity between White and Ground = 0009 Ohms


Are these readings okay?

Cheers, Thanks so much

Kieran
____________________
Cornwall

[stinkwheel]

[Kieranroberts...]

Hello again,

Thanks for you fast reply! i fully understand it now!
You have helped me out so much! I really appreciate how helpful you have been!

The wiring diagram for the earlier CG125 is exactly the same wiring layout to my bike!
i have no CDI or resistor on my bike at all because of this.
My bike defiantly is setup for 6V!

There are points under the flywheel yeah, with a condenser.
these are both parallel to each other, it defiantly isn't a 12v stator with 6 coils arranged in the circle.

Also, i Looked up my VIN from the frame and V5C and they do match and is a 1996 frame. However the the engine number from the V5C is different to the on on the actual engine!

They both start out the same but the last 4 digits are different to each-other, (ive put stars where the digits go to be safe, im not sure if these are numbers i should be sharing online?)

V5C - JC18E-500****
Engine - JC18E-500****

With some reading online last night, i did find that JC18 is the start number for CG125 engines made in the year 1995/1996.

and also that you cant fit in 12v stators in place on 6v as then the flywheel cover dosent fit back on?
I think maybe whats happened is that in the past is the original stator was bad and maybe someone in the past couldn't source a 12v one so they put an old 6V one on and removed the CDI?

My flywheel does have Brazil stamped on it if thats any help too.
Now, with Your knowledge we've found out what the problem is,
Whats the best way to fix it ?


I have been working on my bike getting it ready for an MOT for days now and want it to be on the road very soon.

All my bulbs ands stuff are 12V, i have one set of rear small LED indicators, all the rest of the bulbs (headlight, front indicators, tail light etc...) are incandescent though.

my battery is 12V and the compartment for it is custom and it fits in there really nice, a 6V battery wont fit in there without modification.

I know you can convert 6V to 12V by replacing the stator, buying a new Regulator Rectifier, and then im guessing a CDI unit for ignition?
This sounds like its going to be expensive and sourcing the parts isnt that easy. Is there a universal stator i could use?

Is there some kind of way to do this without replacing the stator and just swapping out the RR for a 12V one? and running the lights straight from AC?
I know its not correct way to do it but it could work?

I dont really mind if the lights are dim, im not looking at having super bright lights and dont really mind this as i would only really be driving the bike in the day and only occasionally in the evenings. (short distances).
can the current Stator put out enough to charge a 12V battery if some wiring trickery and a 12V Regulator Rectifier was done?

I really dont want to go and buy a 6V battery and all new bulbs.
£20 on a 6V battery and trying to source 6V bulbs now and in the future is hard and also expensive. It adds up to just as much as a 12V conversion if im not wrong?

Appreciate any help!

Thank you so much again!

Cheers! have a good one!
____________________
Cornwall

[stinkwheel]

Can be converted back to 12v but you'd need a CDI and replacement generator assembly, would be expensive. As you've seen, the current stator can only do 8 and a bit volts.

I'll get back to you in a bit, sneaking in posts at work. I would personally stick to 6v because you have a running engine! Full 6V conversion would be easy.

Look at www.tayna.co.uk they list batteries by size and capacity.
____________________
“Rule one: Always stick around for one more drink. That's when things happen. That's when you find out everything you want to know.”
I did the 2010 Round Britain Rally on my 350 Bullet. 89 landmarks, 3 months, 9,500 miles.

[stinkwheel]

Hey, panic over!

Just found out there were 12v models with points and 2 coils from the early 90's and yours probably is one of those. Anything after '95 should be CDI according to everything I can find though...

I wonder if it's had a parts/engine swap or was simply an old stock one. It's 24 years old and you have non-matching engine numbers so some sort of shenannigans have gone on somewhere

Does your reg/rec look like this? Should have a part number on it starting "SH", then a long number then either "-12" or "-6" denoting 6 or 12v
https://images.wemoto.com/full/REGULATOR_RECTIFIER/10003719.jpg

And you have two coils on the stator.

Oh, look what I found! A workshop manual download:
https://die-kleinkraftrad-ig.de/wissensdatenbank/reparaturanleitungcg125.pdf

Could be a duff lighting coil after all. Or maybe someone has swapped in a 6v coil or stator plate? Not exactly sure how you could tell. The BR part number suggests it's a 12v rotor. The resistance and voltage readings you are getting are consistant with those on my 6v honda H100. The manuals are very vague on this point though. They do say to test output at higher revs with the headlamp on full beam.

You MAY be able to get a brand new 12v lighting coil that will fit. Not listed as a CG125 one but maybe it will fit? Worth giving them a call: https://www.electrexworld.co.uk/acatalog/L25.html#SID=1150

Failing that you could get it rewound.

EDIT: Also check you don't have a short on any of the lighting wiring. Take the bulbs out (don't forget the instrument panel and hi-beam repeater) and check there is no continuity between the brown, blue and white wires coming out of the lighting switch and earth. Amazingly, they don't always go melty with a short, I think because they are so weedy.
____________________
“Rule one: Always stick around for one more drink. That's when things happen. That's when you find out everything you want to know.”
I did the 2010 Round Britain Rally on my 350 Bullet. 89 landmarks, 3 months, 9,500 miles.

[Kieranroberts...]

Hello,

I cant thank you enough for your time and helping me out on this !
I really appreciate it!

my Regulator Rectifier looks exactly like that and "SH" code does end in 12.

This morning i started my bike up with only my ignition wire (black + white) connected (obviously) and left out the Yellow and White cables.
with the bike at highish revs,
(no rev counter but would say around 2000? enough to take off in first gear)
Out of interest, i connected my headlight straight to the yellow and ground and then white to ground,
(No Regulator Rectifier in the circuit) both made the bulb shine very bright) i left it at that and didn't do a AC reading. Silly me.

This afternoon (just now) i did the same thing but with one of my LED indicators. As i was curious if what i thought my 6V system would do with LEDS as it managed to shine my headlight very bright (LED could be dimmer maybe? if anything?).

With the Same, maybe higher revs. (Possibly up to 3000)
Yellow to ground with the LED glowed bright as 12V should, not dim at all?!, I tried white to ground and then blew the LED haha, Silly me for not testing the AC first again. I then connected straight to my 12V battery on the workbench and the LED indicator was so dim, defiantly blew it, poor thing .

with the bike still running at the same revs i did an AC test,

Still no Regulator Rectifier in circuit...
Yellow to Ground = 25V ish
White to Ground 35V ish
I think i got up to 40V on the white to ground at one point.

I think i know why my poor Little LED blew

i was Lowering the revs using the mixture screw, this decreased the voltage, (as expected?)
at around idle revs, possibly a tad more to keep the bike running whilst testing, I was getting:

Still no Regulator Rectifier in circuit...
Yellow to Ground = 10/11V
White to Ground = Can't remember but think it was slightly higher (around 12V) could be wrong.

This sounds about right?

I think it went down to around 8V/9V when the bike was just about ticking over/ Chugging before it cut out.

I have been reading through that exact same manual online to help me with other bits and its been very helpful and useful, it seems to have a mix match of years etc and mostly only showing 1980 to late 1980's CG125 configurations though but still, same principal on most of the parts .


I'm Possibly thinking it could be the Regulator Rectifier that maybe isn't functioning correctly?
i will do another DC? test soon from the outgoing Red to Ground? of the Regulator Rectifier to see what voltage im getting there.

im also thinking that surely as the bikes being ridden, the revs used will never let the voltage from the Generator drop below 10V minimum? Possibly at traffic lights/ when stopped? I really don't know at this stage as i've never ridden the bike apart from up and down the road when i bought it a couple weeks ago. and other factors including that im new to motorcycle electrics

Again,

Thank You so much for Your help and time! Your easy explanations are exactly what i needed to get my head around what's happening here!

Thank You!

Cheers, Have a good one

Kieran




EDIT: ive just now literally started my CG125 and did a DC test from the Red wire to Ground, (battery disconnected).
I was getting around 7.5V/8V and about 9V with higher revs.
Again, being new to Motorcycle Electrics, i don't know if this is correct or not. I had reason to believe that that test should be outputting over 12V whether the battery was connected or not. If you were not giving that 12V battery over 12V to begin with, how would it charge? Am i being silly?


I tested my headlight (Red to Ground, straight from Regulator Rectifier, It glowed, Dim though. Attaching my other LED's, the LED's worked fine (headlight bulb test disconnected). Maybe slightly dim but still pretty good, 7.5V worked fine! happy with that.

Anyway, I decided to connect my battery to the Red from the Regulator Rectifier and to ground, as normal, the way the battery is supposed to be connected.
I had 12.00V on a DC test on the battery on the workbench.
After connecting the battery up as it should be, with the bike running at idling revs, the DC multimeter was reading 12.30V/ 12.40V. Good news?

Increasing the revs to similar as the test earlier today (2000/3000) i had about 13.5V on the battery terminals.
All seems to be in order now?

After running the bike with the battery connected for about 2 minutes, i disconnected it and did a DC workbench test again, 12.34V.

Brilliant! Battery is charging! System seems to work Fine and as should!

Well happy!

I don't know what was going on before and what's happening now but all seems to be working great!


I think being New to Motorcycle electrics played a part and having knowledge of domestic electrics confused me a little as they seem to be quite different ! also never working on anything lower than 230V AC.

I really hope the problem was being being an idiot and thinking the worst! Most Probably!


Thanks for all the input in helping me out! im sure id still be scratching my head and thinking something was wrong if you hadn't helped me! im hoping its not!

Your post just before lunch gave me much needed confidence that early 1990's CG125 Models can have points etc!

I was starting to think it defiantly was a 6V Generator/ Stator!

Hopefully it continues to work as i just had it working whilst testing.

Thank you again for being really kind and helpful!

Cheers, Have a good day!!
____________________
Cornwall

[stinkwheel]

13.5V seems much better. I'd ideally like to see it a bit higher but yes, it's charging The battery doesn't actually drain unless you're using the brakes/flashers anyway.

I wonder if there was a bad earth/live connection somewhere and you've cleared it up plugging/unplugging stuff?

It's a contrary system and an old (read late 1950's) way of doing it. They don't do it that way much on bikes any more.

You CAN get a 12v AC regulator if you want to avoid the risk of popping bulbs. The lighting voltage is only regulated by virtue of there being enough bulbs to soak up the available power. It's a stupid way of working it. If your headlamp pops, all the others will follow.

If you want a belt and braces test that your battery is charging, connect your ammeter in series with the battery positive and run the engine. (remember to use the 10A jack, or use a clamp meter round the battery positive if you have one).

It always occurs to me that it should be possible and relatively straightforwards to convert the whole damned thing to DC and use LED bulbs throughout. You'd just need to disconnect the yellow from the headlamp switch and attach a black (switched DC live) in its place, there's even a space on the black multi-terminal in the headlamp. Then the headlight would work even if the engine is off. Trouble is, without an LED headlamp, I don't think it could charge the battery as quickly as it discharges.

I did this on my recent enfield build (fitted with an extremely weedy generator for reasons I won't go into just now). It draws 2A with ALL the lights on at once and has a headlamp that's better than the 55W H4 halogens fitted to modern bikes. About £70 of bulbs/relays though (the headlamp bulb was £40 by itself). Maybe after the MOT though eh?
____________________
“Rule one: Always stick around for one more drink. That's when things happen. That's when you find out everything you want to know.”
I did the 2010 Round Britain Rally on my 350 Bullet. 89 landmarks, 3 months, 9,500 miles.

[Kieranroberts...]

Hello Again,

Thank you for the reply again!

Correct me if i am wrong but will this work:?

The way i am thinking about wiring this is pretty much the normal way anyway (i think) but;

-Yellow from Regulator Rectifier to feed the Light switches for headlight and tail light, and thats all that the Yellow wire will feed.
(Risk of blowing Bulbs but i presume that is normal with CG125's wiring in this stock way?)

The 12V AC Regulators, with a quick search i can't seem to find one online, these are not nessacary, just a precaution, is that right?
Surely at some points there could be 35V+ going to these bulbs?!
Are all CG125's like this?



-Black Switched DC live to feed Indicators and Horn.

Now, Speedo Illumination, Yellow or Black Switched DC Live? Which is best?


Good idea with Switching it all the DC, With using LED's in all lighting points, i might go onto this idea if i have any problems with bulbs blowing etc.

Thanks so much again for your help!

Cheers again!,

Kieran
____________________
Cornwall

[Kieranroberts...]

[Easy-X]

Lol.. just noticed the location Penzance?
____________________
Royal Enfield Continental GT 535, Husqvarna Vitpilen 401, Yamaha XSR700, Honda Rebel, Yamaha DT175, Suzuki SV650 (loan) Fazer 600, Keeway Superlight 125, 50cc turd scooter

[stinkwheel]

You don't actually need an AC reg. They've been using that system as-is for decades. It would just be a refinement, I just find it inelegant, even old vespas use an AC reg for their direct lighting.

In theory it should blow the bulbs at high revs but they have balanced it so the combined wattage of the bulbs uses up all the power it can deliver. The yellow also goes to the reg/rec when the lights aren't on and helps charge the battery. Some LEDS will work with AC but you need to use filament bulbs because otherwise the LEDs can go over voltage and pop (as you saw). Filaments (broadly speaking) need to go over current to pop. Totally fine to use LED indicator bulbs though (with an appropriate flasher relay).

From experience of the 6v ones, if you run it with the headlight on all the time, the battery slowly discharges, then the flashers and horn only work properly when you are doing more than a certain rev speed. In countries where a headlamp is mandatory all the time, they added an extra coil.

If you think this is basic, the really early ones just have a diode in the charging circuit to half-rectify it and no regulator at all, they rely on the battery to damp down voltage fluctuations.

Speedo backlight has to be on the same circuit as the headlight , otherwise it won't come on and off with the light. If you attach it to the DC, it'll be on all the time.

Later models had a more conventional 3-phase alternator with everything powered from the battery. Some even have electric start. The points ignition has advantages though, it "self excites" so the engine will keep running even with no battery or if the main fuse blows. They get you home (and can usually be fixed at the side of the road if they malfunction).

All theoretical though. Get it through the MOT left standard, get it on the road and see how you get on with it. It's much more fun to ride them than piss about with the electrics. It's only in the last couple of years that LED headlight bulbs have become good enough to be a properly viable alternative.

The headlights ARE shit in the dark though, 35w tungsten filament. Mrs stinkwheel once got pulled in by the police on her little 100cc Yamaha (same headlight) because she was riding along the white line in the dark so she could see where the road went.
____________________
“Rule one: Always stick around for one more drink. That's when things happen. That's when you find out everything you want to know.”
I did the 2010 Round Britain Rally on my 350 Bullet. 89 landmarks, 3 months, 9,500 miles.

[Kieranroberts...]

Hello,

Thank you for the fast reply again!

The headlight installed on my bike is a aftermarket round one with a H4 bulb inside (12V/55W) and the tail light has got a normal (12V/5W).

So this should be fine im guessing?

Also in theory, if i do get a problem with bulbs blowing often, i could just install and extra 12V, 4-pin Regulator Rectifier "inline" in the Yellow wire which will Regulate the High AC output from the generator to a "consistent" 12V? Bit of a "hack" but im sure would work?
(of course after find the right "input-output" + ground? terminals of the extra Regulator Rectifier?)

I found a decent looking Regulator Rectifier on eBay for about £5.

I have attached a photo of the eBay Regulator Rectifier.


Thank You Again!

Cheers, Have a Good Day!

Kieran
____________________
Cornwall

[stinkwheel]

[Kieranroberts...]

Hello,

Sorry i didn't reply yesterday!

Thanks you for Your reply! I really do appreciate how helpful You have been!

Yeah, that totally makes perfect sense about to 55w being dim and 35w being incredibly bright.

I guess the next step is to try and use the 55w at night time and see what its like and then if its too dim, i shall try to get a H4 35W Bulb from Halfords.

Also, Makes sense about a AC-DC 12V Regulator Rectifier loosing half the power!

Thank You for Your Help again!

Cheers, Have a good day!

Kieran
____________________
Cornwall