Honda CG 125 1980 electrics problems, HELP!!

[RogueCarl]

hey all, im new to motorbiking, only passed my CBT a few months ago, bought a cg 125 from 1980 and then crashed on my first day riding, it wasn't my fault that a herd of deer jumped out, but that's besides the point.
i've been fixing it up since, and the mechanical side of it is fine, but i keep getting niggles from the electrics and i just can't find the solution!
1st problem - it all works but the brightness of the headlight matches the amount of throttle i give it until the bulbs blow (i've replaced the rectifier and checked all the earths i can find).
2nd problem - i indicate left or right and they're the perfect brightness, but then i apply the brake and it seems to steal the power from the indicators and they stop, but then i release the brake and they're just flashing dimly, they don't brighten again until i turn it off then on again.

has anyone else ever had this problem? if so i'd like some help!! D:
and alas, being a student i'm poor so would prefer not to go to a garage and pay someone else to do it -.-

cheers, Carl

[numpty2]

You should be able to sort all this out. There is loads of stuff online for the CG, and there is a Haynes manual.

1980 - Does that mean it is the original 6v model, or the later 12V?

Is the battery OK? A CG battery will be cheap. Bitzforbikes is listing a battery for a 1980 model at £20. I had a CG125 for many years, and the battery does need to be good.

On the plus side, the electrics on these are very simple & easy to work on. Spares will certainly be cheap. I do know the electrical system is quite weedy, but it is up to the job.

A cheap multimeter will be very useful as well. Congratulations anyway, CGs are wonderful.

[neil.]

Have you got a multimeter? What is the battery voltage with the engine off and then again with the engine running and the throttle held open a bit to increase the revs?
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CBT February 2008 | A2 June 2008 | Yamaha YBR125 (written off) | Honda CBF125 (current)

[RogueCarl]

That was quick!
I do indeed have a multi-metrt, it reads OV when turned off, and a constant 5.96V when on and/or throttle on.
I have the haynes, and we've been through all we can see to no avail. I'm inclined to believe a wire for brake light power is crossed with a wire for indicator power, but i can't see it anywhere

[numpty2]

Right, so it is indeed the old 6V version. Later models are 12V.
I think you might find yours was made in Japan. Later production moved to Brazil.

I don't have much experience with 6V systems. I would have expected you to get around 6-6.2V with the engine not running, and maybe 6.5V with the engine running.

Anyway if you are getting 5.96V with the engine running, but 0V with the engine off, it sounds like the battery isn't actually holding any charge whatsoever. If so, that battery is completely gone.

Take the battery out of the bike and check again with nothing connected. Do you have access to a 6V battery charger? You could leave it charging just to make absolutely sure.

If the battery really is this knackered, it would explain the issues with the indicators & brake light. The battery is needed to act as a reserve to cope with such high demand situations. If the battery is knackered, your poor little alternator simply can't cope with demand. A knackered battery might even be draining power, but giving nothing in return. It's just too much for the system.

Some people change these bikes over to 12V systems for better lighting, but I don't think you need to rush into this yet, particularly given your budget.

So it looks like its new battery time, subject to further checks. Not too expensive really, but make sure you get the right one for your exact model.

[RogueCarl]

Oops, my mistake there, i've checked it again and it does read 0V when switched off and/or detached from the bike.
Slight tangent - do you need to charge the batteries? I recall my uncle charges his every few weeks.

[RogueCarl]

6V when off. Third time lucky.

[stephen_o]

I had same problem on my 1979 C50, only trouble is it was 23 years ago. I had to replace the battery as the original had boiled dry, I think I also replaced the recifier and maybe a condensor? not sure now but it sorted my problems out

[RogueCarl]

I've replaced the rectifier already, the battery seems to be fine, i haven't checker the condensor yet i dont think. How am i to check that please?

[WetSparks]

First thing I would say is to check your multi meter technique to ensure the readings are valid, little things like making sure the meter is set to read DC voltage rather than AC volts.

1st the headlight problem. If the brightness is rising with the revs, set the meter to DC volts and put it across the headlight bulb and check what the voltage is, min and max revs. If as your saying it gets brighter with high revs it would be nice to know what the max voltage is here. This problem does smack of a non working regulator though.

2nd the indicators. The fact that they dim/go out when you apply the brake does sound like an earth fault. Maybe temp run a wire from the brake light ground to the battery Neg -, to prove this out.

3rd the battery. It seems you have a lower on voltage than off, this again is a possible fault with the reg. Check the voltage at low and high revs and let us know what they are.

Not sure if you have a 3 phase alternator on that bike or not but, if there are 3 wires coming out of it to the regulator then the answerer is yes. Check the voltage between the different pairs and to ground from each and let us know what they are. Ohh, don't forget to set the meter onto AC voltage to measure the voltage at this point.

[la_lucha]

I have a 1979 with exactly the same issues. So i'll watch this thread with interest.
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Feck Orf

[RogueCarl]

Excellent, i'm working tonight but i'll check all of the above asap and let you know the results sharpish. Cheers

[finpos]

The headlight runs directly off the alternator and bypasses the battery and regulator completely, which is why it becomes brighter with revs and dims to nothing on idle. With the engine at full chat it's subject to the full output of the mighty altenator in AC which may well be over 50V! You need to make sure that both the bulbs (tail, head) are the correct rating, and you also need to make sure that the ballast resistor, which does the job of damping down the worst of the alternator's excesses is doing it's job. The ballast resistor is a huge, wirewound thing normally found behind the little plate that says "honda" on it across the front forks. you need to make sure it's connected into the headlight circuit and that it still shows some resistance to ground. (more workout for your meter skills)

The problem with your indicators is that the battery is much more borked than you think it is.

f.

[Itxi]

I have a 1978 CG with these issues (apart from the headlights blowing), watching as well

The condenser isn't linked to the lights, only the ignition so unless that's not working don't worry about it.

Also I have replaced the regulator on my bike and that didn't help with the problem, though it seems to be lessening so maybe the battery is slowly charging now. Have you checked the actual output from the alternator?

[lisayling]

yeh, i think it is useful,which can be adopted

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[RogueCarl]

im back!
dad called me today and said to go for a short ride around the lanes on the bike to possibly charge up the battery a bit, so i did this and checked the voltage at different stages before and after the ride. here are my results:

before, bike turned off: 4.9V
before, bike on: 5.2V
before, bike on, throttle on lots: up to (maybe over) 9V
after, bike off: 4.2V fluctuating as low as 3.8V

now this should be a 6V battery. my next step is to replace the battery i believe, but this'll incur the cost of the battery and a charging device so i'll check with you guys before i go spending for no reason.
what do you think? thanks

[finpos]

Battery is borked, but check it's not just become dried out - you may bring it back to life if it is - just fill it with water.

Next regulator may be borked also but you won't even be able to tell unless you know for 100% sure your battery is ok first, which you do not.

Finally, you won't need to buy a charger for your new battery it'll be good enough out of the box.

f.

[numpty2]

Yes you shouldn't need to buy a charger, given your finances.
A new battery and a good run should sort it out.
If you do need a charger, try and borrow one. There's bound to be someone on this group who has one you can borrow. I think I've got a 6V charger in my shed that I will never use.
Tell us what town you are in, and see who can help.

[RogueCarl]

Right, i've ordered a new battery and charger (i got my dad to assist ) and they should arrive next week. I'll fill it up, charge it and attach it then let you all know the results. Hopefully this'll be the answer. But i wont get my hopes up too much as there have many 'this is it!' Parts.

[RogueCarl]

Hi all, i'm back from the tense wait. i got a 6N6-3B battery from whitedogmotors with a charger. set it all up and charged it (which was easier than i had expected after reading all of the safety warnings). after it had finished i put it in the bike and took the readings:
off of bike: 6.6V
in bike, bike turned off: 6.6V
in bike, bike turned on: 8.5V
in bike, bike turned on, throttle on: 8.5V

i found this quite bemusing as it's only a 6V system.
it only managed to fix (slightly) one of my problems, so now when i indicate and use the brake it still takes the power from the indicators, but now returns them to the same brightness once i release the brake.
i still have the brake stealing power from the indicators though, and the same problem of the light increasing in brightness with the throttle being on.

HELP!!! any further suggestions?
on the bright side, i can now ride it to work

[Itxi]

I think the light increasing in brightness with the throttle is just a 6V thing, nothing can really be done about it. But provided it's bright enough when the throttle is low nothing wrong, just means you're easier to see when you're going faster

[finpos]

[RogueCarl]

okay then, that all seems to make sense.

i had a thought earlier, could the specific gravity of my electrolyte be slightly high? as the readings i got were a little too high also.

so you're saying that the brightness increasing with the throttle is unfixable? because i don't particularly want to blow the bulbs again when i turn it on in the dark for coming home. it was horrible riding back last time with only my park light

cheers

[finpos]

I wouldn't worry too much about your specific gravity, if it's not right now (in a new battery) it never will be.

You'll just have to try the headlight, preferably before you really need it. It will always be dim at low revs and bright at high, but obv. should not blow bulbs. There is some chance that the new battery may have helped things but if not you are back to checking the bulbs and resistor as mentioned above.

f.