CG125 Headlight

[speedingmotor...]

Hello BCF

the headlight on the 80 CG125 isn't working all other electrics are fine, i have changed the bulb and still nothing at the headlight. i was wondering, besides at the bulb, where could i check with the multimeter to find whats wrong. i have the wiring diagram but dont really know whats best to look for. perhaps there is something wrong at the handlebar switch? or further back on the circuit?



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[AndyCF]

Does the side/parking light inside the headlight work (if its got one) ?

I'd start with the basics first. Check any fuses and unplug the headlight connector.

Switch your meter to a 12v DC range or thereabouts.

Stick the negative multimeter probe onto a good earth point like a clean bolt or the battery negative terminal.

Now probe with the positive multimeter terminal each of the three pins of the headlight bulb connector. With the headlight on dip and then with it on main/full.

You should have power at one 'pin' at one setting and power at the other at the other setting.

If this works, the pin that did not have any power on at all, connect the multimeter negative lead to this then probe the other two pins (dip / main) in turn.

I'm assuming you've had a quick look at any multiplug connectors first (if not unplug them and examine them for corrosion etc)

[Teflon-Mike]

Have you started the engine?
AFAIK all UK* CG's had what is known as 'AC Direct' lighting. Electricity is taken straight of a windng in the generator and sent to the headlamp bulb and stop lamp bulb. It is not taken from the battery, and it is entirely unregulated or rectified, hence you gt a pulse every time the magnet on the crank passes coils on the stator.. so if no engine revs... no lights.

That's the firt 'dumm' out the way.

Next one is what did you change the bulb for? Was it correct voltag? Early CG's are 6v.. if you have 12v bike, could have blown moment you swtched it on.

The OE blbs, OTMH are also very low wattage, 25 or 35w... if tick-over low they can dim or flicker because the generator isn't powerful enough to light up anything more, so fitting higher wattage bulb say a 45 or 55w will oft have the oposite effect to desired and not provide any more light, because generator simply doesn't make enough power to make t more than glow, and again, at tick-over revs possibly not even eough watts are escaping the generator to make it glow.

Next up, check fuse.

Then you say you have been working headlamp.... check connections, particularly the chassis earth, through the headlamp bolt ad stay to the forks,, easy to dislodge wires there when removg headlamp lens to get at the bulb, also easy to dslodge them putting it back, whe you cant see them.

IE start with the basics... and work logically.... and before looking for more than standard,,, make sure you have what you should as standard.

I would be reaching to turn the kettle on, and find the 'dumb' long before I started reaching for my mult-meter....

* I believe all early 6v CG's were AC direct; later 12v models I velieve were, at least until the end of 'official' brazilian supply to UK. Some paralell ported Japanese 'nostalgia' odels had some differences, as did turkish and chinese built examples, some of whch, like the many Chnese CG copes and dervatives, which have often provided parts and 'upgrades' for earlier models, may have had rectified, 12v battery supplied lights.
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[speedingmotor...]

thanks mike and andy for your advice

i checked the fuse, the cable was a litte corroded where it entered the fuse holder, clipped and replaced it and then check and cleaned the two plugs below, the white pinned plug was kind of nasty.

turned the bike over, let there be light.

thanks alot for your advice, i know the cgs can have electrical problem and most of the time relatively easy to diagnose, thanks for clearly explaining your troubleshoot approach


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https://www.youtube.com/watch?v=zojEIR_SGSk