No spark Honda CG125

[Jetskiover]

Have just used a 6v battery and tested ignition coil. If i earth the coil body to neg on batt and hold spark plug to body of coil. Then touch positive wire from coil to posative on batt I get a spark at plug so ignition coil is good.

[Jetskiover]

So 6v from generator to coil and ignition coil works but no spark when ignition coil is bolted to frame.

[ThePhatomfart]

Think your getting there now matey, how about a separate wire running from an earthing bolt on the coil straight to a good earthing point on the frame, see how you go with that ,

[Jetskiover]

Already tried that but no good.I thought it may have been bad earth on engine bracket so have cleaned them up to bare metal !!!

[ThePhatomfart]

maybe's we are missing something, and may have to re-install the battery into the system, just to enable a proper + and - route around the frame , seems the circuit isnt being made, as lights work off the Gen you wont need that , but maybe the Ignition Switch and possibly bypass it, the Silicon Rectifier is enable through it, dont know what you want to do with this bike , is it a full restore?

[fastbob]

In my experience of CG 125 s with no spark it is always the generator stator windings that are at fault . Without the bike actually running , it is not possible to test the output just by kick-starting the bike . I used to send mine off to a chap in Teignmouth to have them rewound but I can't find anything about him on the net . Try this place . http://www.bbbikeshop.co.uk/acatalog/info_1271.html

Edited December 30, 2019 by fastbob

[Jetskiover]

The weird thing is the only thing I done is removed the head and barrel. Before doing this I had a spark at the plug.

[Jetskiover]

I didnt have the battery fitted in the bike when I had the spark at the plug. Only thing i have done is removed the head and lifted the barrel.

[fastbob]

Ok , try this . Remove the steadying brackets from on top of the engine and scrape the paint off them and the frame where they make contact and bolt it back on again . It is actually possible that the cylinder head has no pathway to earth especially if the head gasket is of the composite type .

[fastbob]

Have you tried holding the plug against the CRANKCASE when cranking the engine ? That head gasket looks like a pretty good insulator to me !

Edited December 30, 2019 by fastbob

[Jetskiover]

I have cleaned all the brackets holding the engine. Also cant understand why the black /white wire would spark when touching the head if it was the head gasket !!!

[fastbob]

Ok , something else to try . How about swapping the stator coil wires over so the top one goes to the coil and the bottom one goes to battery and lights ? I did this once and got a spark .

[Jetskiover]

Thanks. Will give it a go but before removing the head and lifting the barrel it was the black/white wire that was connected to the ignition coil and created a spark at the plug.

The only other thing i can think of is the o rings on the head bolts but its a long shot. Plus why would the black /white wire spark if coil doesn’t !!!

[fastbob]

Beats me ! Sounds like you know your stuff so I don't know what else to suggest . I'll dig out my manual and have a think about it . What about the capacitor ?

[Jetskiover]

Have just tested the ignition coil off the bike with a 6v battery and got a spark at the plug.

[ThePhatomfart]

Been looking thro the manual, and always seems to come back to the points, when you put everything back together and adjusted the contact breaker gap ,did you put the insulated washer back in the right position, I know its obvious but if your like me in the rush to get it going things can be missed

[Jetskiover]

It’s got to be something obvious but the fact that the black /white wire will spark when held near the head and kicked over is making me think its not related to points ?

6v at connector on black/white wire and ignition coil checked and 100% ok. Leads me to think its when coil is bolted to frame but earthing of coil to frame checks good too.

Will try earthing coil remote from frame and kick over and see what happens.

Am very confused !!!!!!

[ThePhatomfart]

Page scanned from the Manual

scan.pdf

[billy sugger]

time for some thinking outside the box. the brackets that hold the coil pack to the frame should have spacers behind them so a distance is maintained between frame and HT coil. it may be possible, if you do not have the spacers, that the coil is arcing to the frame rather than at the plug, as current will take the path of least resistance

[Jetskiover]

Sadly I already have the original spacers fitted under the coil.

[Jetskiover]

Have confirmed the ignition coil is working correctly by using a 6v battery remote from the bike and got a strong spark on the spark plug.

[ThePhatomfart]

Then it must be down to the Earthing,did you try an earthing wire from the bracket to maybe a bolt on the engine,should be the best earth you could get

[Jetskiover]

Thanks I did try this but am going to try it again as it must be something obvious !!

[ThePhatomfart]

Yes as you know its always a problem trying to solve by remote, always better when you can look over a shoulder

[Jetskiover]

For sure. I keep going back to the fact that it was ok before removing the head on the engine !!!