Honda CG125 ES no spark

Hi guys new to this site so I'm hoping that someone clever out there can help me get a CG125 going again.

So I have a CG125 ES 2007 Brazil bike, was running fine then one day wouldn't start.. Basically it has no spark!!

I'll list the things I've checked

Plug is new.

The coil all metres out primary and secondary sides.

This model has the CDI that takes the 12v live direct from the ignition live and has an ignition trigger/pulse generator by the stator.

I've metered this out and it's 220ohms so that seems ok. All wiring has continuity plug to plug and the earths are all good.

The CDI has the 12v going to it when the key is turned but when you crank it over no 12v at the coil itself, infact no 12v out of the CDI???

I have tried 3 different CDI's but still no spark. I'm confused and fed up now.... Anyone know if I'm missing anything or if there is something I need to do or buy?

HELP!!

kill switch or kickstand switch faulty perhaps?

Edit: or clutch switch

Well you certainly seem to know what you're talking about and you obviously know how to use a multimeter . I've rebuilt a lot of CG's in the past and when there was no spark the cause was always the same thing , the Stator Coils had gone crispy and broken down .

Thanks for the replies, there is no kill switch or sidestand switch on these models so that rules that one out, cheers tho.

just looked for replacement coils on fleabay and most of them are from china

Is page 101 the correct wiring diagram? http://diagramas.diagramasde.com/otros/honda%20cg%20125%20titan%20ks-es-kse-cargo-manual%20de%20ensamble-103%20pag%20(esp).pdf

Is page 101 the correct wiring diagram? http://diagramas.diagramasde.com/otros/honda%20cg%20125%20titan%20ks-es-kse-cargo-manual%20de%20ensamble-103%20pag%20(esp).pdf

Hi yes that's correct.

I don't know anything about the CG but looking at that wiring diagram it's getting power for sparking from the battery not the stator so make sure you have a fully charged battery. If the battery is fully charged I'd test at the Ignition control module using a test light. A test light is a better test than a multimeter because with a test light you're forcing more current to flow through the wiring than with a multimeter.

At the Ignition control module you've got Red/Black is switched 12V from the ignition, with the test light clamped to ground you should see a bright light when the ignition switch is on and you touch the test light to Red/Black and no light when the ignition is off.

Green is constant ground, with the test light clamped to battery positive, you should see a bright test light when you touch it to the green wire.

Blue/Yellow is the signal from the pulse generator, to test the voltage output of that properly you need a peak voltage detector, but if you put your mutimeter to AC voltage and you touch one probe to Blue/Yellow and the other to ground you should see some sort of reading when you crank the engine. If you don't see any reading the pulse generator or the wiring going to it is the problem. Another thing to check is the gap between the pulse generator and the rotor. If the gap is too big the voltage signal will be low. From what you've described in your first post it sounds like you might not be getting a proper signal from the pulse generator.

I don't know anything about the CG but looking at that wiring diagram it's getting power for sparking from the battery not the stator so make sure you have a fully charged battery. If the battery is fully charged I'd test at the Ignition control module using a test light. A test light is a better test than a multimeter because with a test light you're forcing more current to flow through the wiring than with a multimeter.

At the Ignition control module you've got Red/Black is switched 12V from the ignition, with the test light clamped to ground you should see a bright light when the ignition switch is on and you touch the test light to Red/Black and no light when the ignition is off.

Green is constant ground, with the test light clamped to battery positive, you should see a bright test light when you touch it to the green wire.

Blue/Yellow is the signal from the pulse generator, to test the voltage output of that properly you need a peak voltage detector, but if you put your mutimeter to AC voltage and you touch one probe to Blue/Yellow and the other to ground you should see some sort of reading when you crank the engine. If you don't see any reading the pulse generator or the wiring going to it is the problem. Another thing to check is the gap between the pulse generator and the rotor. If the gap is too big the voltage signal will be low. From what you've described in your first post it sounds like you might not be getting a proper signal from the pulse generator.

Top

Thanks for that I'll take a look tomorrow. I've used the test light on the ignition live and also done that test to check I was getting a good earth, so I know they are definitely all ok.

I'll check the pulse generator tomorrow to see if there is an AC reading. Also if the gap is to big what should the readings be in relation to the normal readings?

Thanks

I'll get me coat .

I'll get me coat .

Can't beat your hands on experience of fixing them. I'm just looking at the diagram and giving an guess what the problem could be. The Cg is an interesting bike. It was made for so long that it shows the development of bike electrics over the years from 6V magneto to 12V points and condenser, then the the different CDI systems. If they made another Cg it would probably be a fuel injected TCI so it would have all the ignition systems.

Maybe it's time they did a current version, it has probably been their best seller next to the C50-90 range

Thanks for all your replies.

So an update on this CG, I have tried 4 different CDI units one off a running bike but still no spark. I have put a meter across the blue and yellow trigger wire on the CDI and earth. When you crank the engine over you get different readings which tells me something is going on at the stator end of things.

There is a constant 12v ignition live at the CDI and the earth wire is good. I've checked continuity between all the other wires and all great. Still no spark, in fact still no live out of the CDI...........

I'm going to throw this in the skip now!!!!!!

fastbob mentioned in another thread about the cylinder head not grounding properly. If you've got a jumper cable you could clamp it from the head to the negative battery post or if you don't have a jumper cable you could take the spark plug out and join a wire to the threads of the spark plug to the negative battery post see if you've got spark with a good ground

Where are you based as a member could be close by and might be able pop round and help out, observing social distancing measures

Re: Honda CG125 ES no spark

Post by dynax » 15 Jul 2020 18:32

Where are you based as a member could be close by and might be able pop round and help out, observing social distancing measures

I'm in Garston Liverpool