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CG125 intermittent sparking

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scotto75
Two Stroke Sniffer



Joined: 13 Mar 2016
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PostPosted: 00:29 - 11 Jan 2017    Post subject: CG125 intermittent sparking Reply with quote

Hi all,

I am having an issue with the ignition on my '88 CG125 Brazil model. The bike can fire up for and run for a few seconds but then dies. It is caused by an inconsistent spark. I'll take the plug out and see that it is sparking fine. Good strong blue spark. I refit and fire it up, but then very soon it dies. I take the plug out again and can see that there is no or erratic sparking. After a while it goes back to normal again. I refit the plug and the same thing happens again.

This is what I know...

1 - I have used three plugs with no change.
2 - I have tried it with a different plug cap with no change.
3 - I have swapped the ignition coil/condenser (both tested perfectly) with no change.
4 - The points have been replaced recently and adjusted correctly.

When I kick the bike over and it's not sparking, the headlight still lights up so I assume the stator coil for the lighting circuit is okay? When the bike does fire, the timing is spot on and the headlight works perfectly, but it only runs for a very short period before losing the spark again.

My next plan is to run some checks and tests on the wiring....

1 - Check black/white wire connections from ignition switch to coil & points. I think it splits from the switch to the coil and points in the headlight bowl so maybe a loose connection there? The connection from the generator to the coil is good.

2 - Check all the grounds - Ignition switch, chassis/frame, coil & generator coil. I'm pretty certain that the grounds for the switch and frame are good.

Does this sound like the right course of action? Am i missing anything?

Any help would be appreciated.
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scotto75
Two Stroke Sniffer



Joined: 13 Mar 2016
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PostPosted: 00:32 - 11 Jan 2017    Post subject: Reply with quote

Oh yeah.... the bike was running perfectly just before New Year's Eve. It was sat for a week outside in the sub zero temperatures. I started it on Saturday for the first time and had this issue.
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jaffa90
Traffic Copper



Joined: 06 Apr 2016
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PostPosted: 00:45 - 11 Jan 2017    Post subject: Reply with quote

Is the spark plug wet with fuel when removed all these times?
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bypass2
Trackday Trickster



Joined: 12 Sep 2013
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PostPosted: 00:54 - 11 Jan 2017    Post subject: Reply with quote

are the plugs you tried new. is the battery good
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scotto75
Two Stroke Sniffer



Joined: 13 Mar 2016
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PostPosted: 01:18 - 11 Jan 2017    Post subject: Reply with quote

My very first thought had been that the plug was getting wet from flooding on startup, but they're dry. I have the plug out and held against the case and can see it sparking intermittently. I replace it with two other known working plugs and the same happens out of the cylinder. The batteries good.
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SixFeetOfMan
L Plate Warrior



Joined: 10 Jan 2017
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PostPosted: 01:28 - 11 Jan 2017    Post subject: Reply with quote

HV cable?
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cbf125
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bypass2
Trackday Trickster



Joined: 12 Sep 2013
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PostPosted: 01:36 - 11 Jan 2017    Post subject: Reply with quote

maybe the killswitch is damp. spray a little bit of WD40 in it and wiggle the killswitch about then try it
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scotto75
Two Stroke Sniffer



Joined: 13 Mar 2016
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PostPosted: 07:43 - 11 Jan 2017    Post subject: Reply with quote

I've tested the HT cable on both coils and both gave good resistance readings with and without the plug cap fitted.

There is no kill switch, or kickstand switch. Just the ignition switch. Not sure if there would be anything internally inside the switch that may cause an intermittent fault?
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smallfrowne
Scooby Slapper



Joined: 25 Jun 2014
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PostPosted: 12:23 - 11 Jan 2017    Post subject: Reply with quote

If the wiring is all ok, connectors, switches, dodgy earths, etc then maybe it's the stator's ignition coil that is bad. Coils can go bad when hot (currently have a very similar issue with a CD250U) and since you've changed the coil pack I'd have a look at the stator.

It might look black and crusty, but maybe not if it's intermittent. Not sure about testing it with a multimeter, I've not got that far with mine yet, so not sure on 'OK' resistance values, but worth a go checking values when its firing ok against when it isn't.

My CG, when it was on points, had the lighting coils fail on the stator. I had no lights but it carried on running to get me home (in the dark Shocked ).

I still have that stator kicking about (nearly threw it out last night). It obviously has bad lighting coils, but the ignition coil worked. Bit of a faff swapping stators about but you can have it for postage if you want to try it.
____________________
'90 VFR750; '89 NC30; '95 DR650; '89 CD250U; ~'82 CG125; ~C90
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scotto75
Two Stroke Sniffer



Joined: 13 Mar 2016
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PostPosted: 14:26 - 11 Jan 2017    Post subject: Reply with quote

I'm going to check the wiring tonight hopefully, although I'm not looking forward to opening up the headlight bowl as it's a proper snake's wedding in there.

I'll probably get to take off the flywheel cover tomorrow, weather permitting, and check the stator coil and wiring then. I'd be well up for your stator coil. If you pm me a price and email to send to, that'd be absolutely tremendous. Thanks!
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smallfrowne
Scooby Slapper



Joined: 25 Jun 2014
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PostPosted: 21:24 - 11 Jan 2017    Post subject: Reply with quote

Right, that took more time than I thought - since I forgot where I put it, doh, only just 'tidied' it away as well - at least it wasn't actually in the bin (I checked Sad )
This look right?

http://i.imgur.com/MdPbp96l.jpg

Snakes wedding - lollers. Any luck?
____________________
'90 VFR750; '89 NC30; '95 DR650; '89 CD250U; ~'82 CG125; ~C90
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SixFeetOfMan
L Plate Warrior



Joined: 10 Jan 2017
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PostPosted: 22:38 - 11 Jan 2017    Post subject: Reply with quote

Top left coil looks overheated to me, sometimes coil overheats inside remaining spotless on the outside.

Scotto75 HT/HV cables usually fail by shorting to earth. Rubber breaks down and spark "leaks" out. You won't detect it with multimeter, you may see cable glow in the dark, or feel it kick as you touch it.
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scotto75
Two Stroke Sniffer



Joined: 13 Mar 2016
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PostPosted: 23:54 - 11 Jan 2017    Post subject: Reply with quote

Smallfrowne - Thanks for going through the effort of digging it out and uploading a pic. Unfortunately it's not the same as mine, as it's only got two coils, not three like yours. Thanks anyway though.

SixFeetOfMan - The ignition coil on it now was a new one straight out of the box which I tested before fitting. The HT should be pretty reliable I guess?

I went through all the connections and grounds and checked resistance and continuity from the ignition switch to the points and there were no faults with the wiring. All's as it should be. I took the flywheel off but couldn't see any obvious issues with either the coil windings, wiring or points.

There is a small oil leak from the crank shaft oil seal, but I can't see that being an issue. I will get my static timing light and double check it tomorrow, but after that I will be properly stumped as to what to do next!
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jaffa90
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PostPosted: 00:27 - 12 Jan 2017    Post subject: Reply with quote

scotto75 wrote:
My very first thought had been that the plug was getting wet from flooding on startup, but they're dry. I have the plug out and held against the case and can see it sparking intermittently. I replace it with two other known working plugs and the same happens out of the cylinder. The batteries good.

Dry spark plugs !!!!!!!!!!!!!!!??????????????????
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scotto75
Two Stroke Sniffer



Joined: 13 Mar 2016
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PostPosted: 00:24 - 13 Jan 2017    Post subject: Reply with quote

Rust on the points!!

I suppose it may have been sat over the Christmas hols with the points open, but somehow a small spot of rust had devloped on one of the contacts causing the points to not close properly. (I have concerns about the negative effects of moisture being trapped by supposed breathable waterproof motorcycle covers).

I have recently moved house and lost my workshop and all my tools are in boxes still, so all week I have been conducting roadside maintenance in the dead of night with the little time I can snatch away. Tonight I finally dig out my flywheel puller and static timing test bulb and stuck a powerful torch on it. I could see they weren't making proper contact, so a little rub with some wet and dry, readjustment of the timing and the bike's running perfectly again.

Thanks for all the helpful suggestions. Much appreciated.
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smallfrowne
Scooby Slapper



Joined: 25 Jun 2014
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PostPosted: 00:38 - 13 Jan 2017    Post subject: Reply with quote

I will sleep soundly tonight. Good stuff Thumbs Up
____________________
'90 VFR750; '89 NC30; '95 DR650; '89 CD250U; ~'82 CG125; ~C90
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