No spark Honda CG125

Hi.

Hope someone can help me.

I have a old 6v cg125 with points ignition I am restoring. It had no spark so changed points and then had good spark at plug. Had to remove barrel as had no compression. No its re assembled I have no spark at plug. Have 6 v at the black white cable from generator . Have tried several coils . It seems to be problem since removing brackets which mount to frame which steady top of engine.

Have checked good earth at ignition coil mounting bracket.

Am stumped !!!!!

Have you checked Points, Timing , Condenser and Ignition switch

Thanks for the reply.

Have set the points to correct gap and get 6v from the black /white wire. The black/white wire will spark on the rocker cover and the bracket for the ignition coil. Don’t have a ignition switch fitted so that cant be shorting out.

Before i removed the valve cover and barrel I had a strong spark !!!

It almost seems like I am shorting the ignition coil out to earth but think the body of the coil should be earthed to the frame !!

I'm assuming you have a pre 85, with kickstart , but which year?

Not sure of the year but it a old 6v version with points.

I have 6v at the connection where the black/white wire joins to the yellow of the ignition coil.

there should be a earth wire between the top engine bracket and the wiring loom

does your coil have a condenser on it

Sorry had to create new account as couldn’t get in !!

I dont think it had a earth wire from engine to frame and yes it does have a condenser on the ignition coil.

I have 6v at the connection where the black/white wire joins to the yellow of the ignition coil.

Check out this thread on another site,could solve the problem

https://www.bikechatforums.com/viewtopic.php?t=176136&postdays=0&postorder=asc&start=0

Sorry had to create new account as couldn’t get in !!

I dont think it had a earth wire from engine to frame and yes it does have a condenser on the ignition coil.

I can fix it! Send me a message and I will sort the accounts out

The weird thing is it seems to be linked to removing the head and barrel as had a good spark nail then.

Have you set up the timing marks against the opening of the contact points

Yes and think its ok. Regardless of when the 6v is created timing wise to coincide with the piston. I definitely have 6v at the connection where the black/white wire connects to the yellow wire to the ignition coil. If I hold the black/white wire to the head it will create a strong spark when kicked over.

Just to be clear, from the Generator, the Black wire to the connector changes colour to the Black/White wire and goes to the Ignition Coil and Condenser, is that what you have, the Yellow wire from the Generator goes to the Headlight control switch

Thats right the black/white is the wire from the generator. This connects to the yellow wire which is the wire coming from the ignition coil/condenser.

No other wires are connected from the generator.

Rightyho, take it its not a OEM part like this one then

https://www.ebay.co.uk/itm/HONDA-CG-125-6-VOLT-IGNITION-COIL-WITH-CONDENSER-30530397003-DIRECT-REPLACEMENT/281802422221?epid=1645310515&hash=item419cbbb7cd:g:nukAAOSwsB9V-owN

and if that coloured wire comes from the coil and condenser then it must be valid with the make, have you tried Primary and Secondary tests on the coil and HT Lead

I have 3 coils now which were all new !! Have done the tests as per Haynes manual and all check out ok.

Have you tried a new spark plug and hung against the block to see if you have a spark when you turn over

Hi. First of all thanks for your help.

Yep have tried with spark plugs and tried with plug cap removed just using bare ht wire.

I am a mechanical fitter by trade but this one has me stumped !!

It seems like the voltage is lost when connecting to the ignition coil as if its being grounded out !!!

no problem matey, would like to get to the bottom of it, so I take it there's no Battery on the bike and you dont have an Ignition switch, so looks like could be wiring and Earthing problem ,with only the Black/White wire coming from the Gen ,6v at the coil/condenser , and you have tried 3 other coils ,there doesnt appear to be a return to Earth, how about looking through the Earth connectors to see if you have a problem there, havent got a pdf manual for this but I do have a paper one , so can grab some pages for you and send pdf if needed

I dont think there are any earth connectors. I think the earth for the generator is via the backplate in the engine. The earth between the engine and the frame is via the engine top steady.

If it was a earth problem then I would not get a spark from the black/white wire when putting it near the spark plug hole and kicking bike over !!!

Right, then the 6v is coming out from the Gen ,but not going through the Primary and Secondary windings to produce the Spark, HT lead and windings tested OK, have you tried pulling off the HT sparkplug cap and earthing while kick starting

Yep. Already tried but no spark !! It’s as though the voltage is lost when connected to the ignition coil. It’s baffling me.