Cg125 no spark

[alun111]

Similar to the other topic, but single cylinder. I thought I'd start my own thread for obvious reasons.

1988 cg 125 BRJ - been standing for a total of about 2 years, I revived it about a year ago by cleaning the carb, putting fresh fuel in the tank and cleaning the plug, it started up with a bit of persuasion.

This time, no dice. I done all of the above, as well as fitting a new plug - no spark.

As far as I know the only things that could prevent it from sparking are.... points, ht lead, cap, coil.

I don't know how to test any of them!

If any one can help me I'd greatly appreciate it, I'm trying to get the bike back on the road for my brother so we can get rid! I've already ordered a new throttle cable and air filter, and I plan on rebuilding the front forks as well as respraying the tank and petsealing it.

Cheers!
____________________
Summer: '00 Honda CB600F Hornet
Winter: '93 Suzuki GSF 400 Bandit VP Variable Valve
Past Bikes: Lifan LF100-5 Lifan LF125-A Honda C70

[Tribal-Wolf]

Here is a manual for it that might help CG125

[alun111]

Thanks but I already have it, and it's confusing and rubbish! lol
____________________
Summer: '00 Honda CB600F Hornet
Winter: '93 Suzuki GSF 400 Bandit VP Variable Valve
Past Bikes: Lifan LF100-5 Lifan LF125-A Honda C70

[Creepin Moses]

Have you checked your imobilizer switch in the stand? sometimes they can cause problems and some people forget the switch is there.
____________________
Bomb disposal expert, if you see me runnin, try to keep up.

[alun111]

Has the 1988 cg 125 even got one?
____________________
Summer: '00 Honda CB600F Hornet
Winter: '93 Suzuki GSF 400 Bandit VP Variable Valve
Past Bikes: Lifan LF100-5 Lifan LF125-A Honda C70

[Pie-Roe]

Ok

As far as I'm aware, points won't make a difference to actually getting a spark, running is a different matter, it's what I got told for a '73 cb125

Check the ht lead all the way back to the coil for any cracks/grazes in the tubing, gently pull the rubber tubing back from the cap and give it a good going with wd40. (in fact take the plug out of both the head and the lead, spray both ends with some wd40, as well as the area around the coil)

Coil, multimeter it, I have no idea what it should be making however.

Pyro
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[alun111]

Cheers, I'll give that a go - any one else?
____________________
Summer: '00 Honda CB600F Hornet
Winter: '93 Suzuki GSF 400 Bandit VP Variable Valve
Past Bikes: Lifan LF100-5 Lifan LF125-A Honda C70

[finpos]

You definitely need to take a look at the points, in your position I'd not muck around and just replace them along with a new condenser.

f.

[alun111]

[alun111]

[nowhere.elysium]

There's a chance that the CDI may be duff.
If the link's a haynes manual, then there'll be a table of results that one should be expecting on the multimeter when testing the coil, along with instructions on how to test the coil. I found it a bit weird on the old CB125TDC, but it made sense after re-read it, and put the beer down...
Also, apologies for asking the patronising question here, but are all the other electrics OK? i.e. Lights, horn and so forth. You've not mentioned the state of them. Could just be a dead battery...
____________________
'10 SV650SF, '83 GS650GT (it lives!), Questionable DIY dash project, 3D Printer project, Lasercutter project

[alun111]

It doesn't have a cdi, it's ANCIENT lol. It runs off points. All other electrics are fine. Battery's been maintained since the bike was stood.
____________________
Summer: '00 Honda CB600F Hornet
Winter: '93 Suzuki GSF 400 Bandit VP Variable Valve
Past Bikes: Lifan LF100-5 Lifan LF125-A Honda C70

[robocog]

Have you checked the fuse? <- obvious stuff first

If ok check for 12v at the coil (or 6v if its that old)
(on the coil there should be a + feed from ignition switch)

Points could be foobarred as already put forward which would stop the coil from making the spark

The coil's HT lead could also be broken, or I suppose the cap

Its a pretty simple system if its anything like my old points CG and relatively little to go wrong so shouldn't take long to sort or turn out too expensive

(worth a quick look behind the headlight for any connections that have come adrift or look bad?)

Will have a look in my manual tomorrow as I'm sure there were resistances mentioned for the coil so it may help you rule it in or out of the equation

Regards
Rob

[alun111]

No I haven't checked the fuse.... but surely nothing would work if that had gone (assuming you're talking about the glass one on the positive lead to/from the battery).

I haven't checked for voltage at the coil... should there be 12v when It's been kick started or just when the ignition switch is on?

So you reckon if the points were out of clearance/stuck/burnt etc it could cause it not to spark then?

I will check in the headlight - I was actually going to do that today but forgot!

Cheers, and I hope to hear from you soon with the resistances (and if you could explain how to check for them that would be great too). Thanks again
____________________
Summer: '00 Honda CB600F Hornet
Winter: '93 Suzuki GSF 400 Bandit VP Variable Valve
Past Bikes: Lifan LF100-5 Lifan LF125-A Honda C70

[baldy]

I'll bet you 2p that it's the condenser or points. They have a habit of conking out after a long time of being stored.

[robocog]

OK, yes the fuse blowing looks like it would stop the battery voltage getting to the ignition switch ,and in turn to the coil so no fuse=no spark from a quick glance at the manual

attached is the wiring diag for our old stylee points CG's

so
check fuse - replace if blown
(a real easy check would be turn ignition key with bike in neutral and see if the dash neutral light comes on- assuming the neutral switch is working and theres _some_ voltage in the battery)

Also worth checking that battery has a good earth against chassis
(green wire)

Looking at the diagram - with the ignition on the black/white wires at the coil should have battery voltage on em, so easy enough to check

See next post for testing the coil..

[alun111]

Cheers mate, much appreciated. The fuse is fine, neutral light comes on with ignition.

I will check the black/white wire. It looks like the black/white wire also takes a feed from the points too. Not sure what voltage this should be though.

*Awaits next post*
____________________
Summer: '00 Honda CB600F Hornet
Winter: '93 Suzuki GSF 400 Bandit VP Variable Valve
Past Bikes: Lifan LF100-5 Lifan LF125-A Honda C70

[robocog]

Not clever enough to do multiple attachments in a single post so please forgive my multiple postings

Attached should be the coil test procedures

It must have been the manual for my CJ that quoted the primary and secondary coil resistances so aplologies for suggesting that I may have them

Hopefully the coil test procedure attached will be enough to prove its capable of generating some spark at least


...just looked closely at the diagram I attached earlier and I think I may be taking complete arse about batt voltage on the black/white line with ignition turned on, also the fuse so apologies for throwing a curve ball there

with ignition on and kicking the bike the black and white wire should have "some" voltage, otherwise its the genny thats bust or points being held closed

a close look shows the voltage may even be ac -directly generated by the generator going to the points and on to the coil and the black white wire that goes on to the ignition switch is infact just grounded to "stop" the engine from running when in the off position
Love it..the more I look at it I can't believe how simple the bike is

so a test would be to chuck a bulb onto the back white wire going to the coil and kick like a mad bugger to see if you can get it to flash?
or a multimeter set to ac volts (one lead to black white wire and other to chassis /earth)
....with spark plug out would help things spin over

Once again sorry for the duff info in first postings, should have at least glanced at the wiring diag before assuming it was anything remotely like any other ignition system I had ever seen before

[robocog]

Attachment went walkies?

[robocog]

I don't seem able to attach any more - perhaps I have hit my quota or something ?
so have popped it on my webserver

https://www.robocog.dyndns.org/cg125/cg125%20coil%20test.jpg

The diagram shows a 6v bulb which I guess relates to the early early CG so if your test battery is 12v I would be inclined to use a 12v bulb
(or a multimeter set to voltage)

Regards
Rob

edited to add I will flip the image the right way up shortly
I'm avin one of those days.. I think I've been out in the sun too long

[Creepin Moses]

Hey Rob, I use Photobucket for my attatchments, then on each pic I want to show here I copy the img code for the pic on photobucket and paste it into my msg here. Photobucket is free for making your own photo albums too.

Davey

https://i300.photobucket.com/albums/nn13/HellRider27/DSCF0290.jpg
See what I meen.
____________________
Bomb disposal expert, if you see me runnin, try to keep up.

[alun111]

Thanks very much for your help, I'll have to give the coils a test at some point... and I'll test the black/white wire with a multimeter set to ac then dc volts with the ign on and kicking it over...

So it could theoretically be the genny that's gone also... but no way of testing if the bike's not running!

If I have no luck I'll take the coil to my mech and see if he can test it. I'm clutching at straws here really but I want to FIND a problem before I start replacing parts just to see if it cures the problem.

Thanks again for all your effort.
____________________
Summer: '00 Honda CB600F Hornet
Winter: '93 Suzuki GSF 400 Bandit VP Variable Valve
Past Bikes: Lifan LF100-5 Lifan LF125-A Honda C70

[robocog]

Maybe
also scanned the genny test diagram and plonked on my server

https://www.robocog.dyndns.org/cg125/genny test.jpg

Unfortunately the manual I have is a bit "iffy" regarding the early 12v brazillians and requires lots of referring to 6v stuff and the genny continuitiy values are not jumping out at me so not sure what resistancy they should be - or it may be that the test as shown is only looking for open circuit issues?

I guess by putting a multimeter to show resistance
one lead going to frame earth and the other to the black/white wire that goes into coil connector

slowly turning engine (by using bolt on flywheel?) should show continuity that is switching between dead short (as good as zero ohms) when the points are closed and some other value (generator coil resistance that is not quoted in my manual) when points open

If the meter is showing dead short all the time when you turn engine over slowly it could well be the points have welded themselves shut?
and if it flicks between dead short and completely open circuit it could be the genny coil is buggered

Good luck and let us know how you get on
The good thing is theres loads of spares for these machines still available and cheap and they are nice and simple to work on

Regards
Rob

[alun111]

The link doesn't work man, cheers though!
____________________
Summer: '00 Honda CB600F Hornet
Winter: '93 Suzuki GSF 400 Bandit VP Variable Valve
Past Bikes: Lifan LF100-5 Lifan LF125-A Honda C70

[robocog]

Sorry its because I left a space in the name of the file

ammended and tested

https://www.robocog.dyndns.org/cg125/gennytest.jpg

Let me know that you can or cannot view it and will sort it out

Regards
Rob