cg125 bypassed ignition. fixed!

Tamsin · World Chat Champion Joined: 07 Mar 2014 Karma :

I'm at my wits end.

The cg125 I picked up recently is starting without the ignition being on. The guy I bought her off told me he had done it (for reasons I believe to be valid, its definately not nicked) and pointed at a scotch lock on the loom.

I've removed the scotch lock and all other non standard wiring and it's still bypassing the ignition.

I can't work it out, there's nothing on the wiring diagram that gives me a clues.

Any thoughts guys?

smallfrowne · Scooby Slapper Joined: 25 Jun 2014 Karma :

What year is it? A load of them have ignition circuits that work like this:

1. Ignition on - Spark signal wire from stator to ignition coil.
2. Ignition off - Spark signal diverted to ground. This stops the coil creating a spark. Switch in 'closed' position.

The switch is 'open' in the on position, meaning that if there is no switch or if the switch is on the result is the same - the coil can create a spark.

I'd check that everything is connected up from the switch, because if the wires aren't connected, that could be your problem - it'll run. But then I don't know when/if Honda changed this setup, and what the hell the PO has put in place to 'bypass' it.

A diagram might help but I'm on my way home in a min... Cool

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'90 VFR750; '89 NC30; '95 DR650; '89 CD250U; ~'82 CG125; ~C90

Tamsin · World Chat Champion Joined: 07 Mar 2014 Karma :

It's a 1995N plate (I believe that makes it an s model) everything seems to be wired up correctly...

smallfrowne · Scooby Slapper Joined: 25 Jun 2014 Karma :

Hmm, ok, I found this diagram i jazzed up a bit some time ago, it's for points but the idea is the same on CDI (up to a certain year probably).

You're interested in the Black/White wire.
https://i.imgur.com/igNs4Pal.jpg
Click for bigah

Plus this other bit that shows how the switch works
https://i.imgur.com/duSU6yt.jpg
ie OFF closes the ignition circuit to ground. E = Ground
But without the switch, the ignition circuit is always 'ON'

I think I got this right anyway, hope I am be making sense.
____________________
'90 VFR750; '89 NC30; '95 DR650; '89 CD250U; ~'82 CG125; ~C90

WD Forte · World Chat Champion Joined: 17 Jun 2010 Karma :

If its an AC CDI ignition bike then not that surprising
as The ignition switch on many CDI bikes just shorts the Source coil output to ground to stop the engine and vice versa.
The Ignition and kill switches, if fitted, work in parrallel regarding this
function.
Disconnecting the wire from the CDI to IGN SW wont stop it running
but might stop it stopping
Easy to debug and put right

If its a 12v coil or DC CDI system then someones been buggering about even more but should still be easy enough to sort out

Honda often use black/white for this wire
BUT
the same colours are used for different igntion systems so
check functions first
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bikers smell of wee

WD Forte · World Chat Champion Joined: 17 Jun 2010 Karma :

Here's what I found for an S/T model
AC CDI
the black/white wire from the CDI to the ignition switch is grounded ( green wire) to stop the engine.
No battery needed if you kick it to start and if the B/W wire
is floating, you'd have to stall it or wait for it to run out of fuel to stop

https://3.bp.blogspot.com/-4XOyyNAc7Fc/VQl6i5jCWXI/AAAAAAAAKro/H8HM7lF8vmI/s1600/003.jpg
____________________
bikers smell of wee

Teflon-Mike · tl;dr Joined: 01 Jun 2010 Karma :

Black white wire earths the coil or CDi.. Ie 'makes' a circuit to kill sparks, rather than brakes it,

Replacement Ignition switches, esp pattern ones often dont include the Black/white wire in the connector block, it's on a separate bullet.

Could it be that pattern switch been fitted & 'loose wire' left dangling?
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My Webby'Tef's-tQ, loads of stuff about my bikes, my Land-Rovers, and the stuff I do with them!
Current Bikes:'Honda VF1000F' ;'CB750F2N' ;'CB125TD ( 6 3 of em!)'; 'Montesa Cota 248'. Learner FAQ's:= 'U want to Ride a Motorbike! Where Do U start?'

Tamsin · World Chat Champion Joined: 07 Mar 2014 Karma :

That's the same diagram I have been working from. The b&w wire is definitely connected in the right place and even if I remove the ignition switch from the mix entirely she still starts.

It's a legit honda switch, or at least it seems to be. The key operates the oggy, tank and the steering lock and it's a Honda key.

MOT is on Friday... :/

stinkwheel · Bovine Proctologist Joined: 12 Jul 2004 Karma :

Tamsin · World Chat Champion Joined: 07 Mar 2014 Karma :

It doesn't have a kill switch.

I'm going to wire one in which will kill the CDI earth if I can't get this worked out in time. Still needs sorting though

smallfrowne · Scooby Slapper Joined: 25 Jun 2014 Karma :

But if you remove the ignition switch, it will definitely allow starting, by (amazing) design of the circuit and switch.
____________________
'90 VFR750; '89 NC30; '95 DR650; '89 CD250U; ~'82 CG125; ~C90

smallfrowne · Scooby Slapper Joined: 25 Jun 2014 Karma :

You could check the switch is ok by checking for continuity between the Green wire and B/W wire in the off position (disconnect the switch first).

If when the ignition is in the off position there is no continuity between these wires then the switch is not a happy bunny. Check that before you go crazy.
____________________
'90 VFR750; '89 NC30; '95 DR650; '89 CD250U; ~'82 CG125; ~C90

smallfrowne · Scooby Slapper Joined: 25 Jun 2014 Karma :

And if you want to stop, just stall. Or pull the plug cap off (probably get a tingle in the finger though).

Triple post madness!
____________________
'90 VFR750; '89 NC30; '95 DR650; '89 CD250U; ~'82 CG125; ~C90

Tamsin · World Chat Champion Joined: 07 Mar 2014 Karma :

That is a bloody good point! Can't find my multimeter but a new one should be arriving tomorrow. I will have a look after college

Teflon-Mike · tl;dr Joined: 01 Jun 2010 Karma :

Simplest kill switch is to take a single wire from the spade terminal on the coil and take it to a good earth.

Make that fast and put a switch in the wire, you have a kill switch.

That is actually how the ignition is actually wired, and why without the wire connected, you cant turn off the engine with it.

I suspect you aren't looking at the right end of the wire, if you are looking at what comes out of the switch, you should be looking for the wire that comes from the CDI, and would be in the plastic multi-way connector block, that the switch completes the route to 'earth' on.

Like I said, sounds like you have a pattern or later genuine Honda igntion switch or lock-set, where the kill switch wire has bee routed parallel to the multi-way connector block, so they can add inhibitors to it, on the bullet connector.

You likely have 8 wires in the multi-way connector on the spur on the bike's loom, and 7 wires in the connector that comes from the ignition switch that plugs into it, and somewhere dangling 'loose' with a bullet on the end, a black/white wire.

If you found the wire i the loom connector block that doesn't have a mate in the ig-switch connector bock; pulled that out of the loom connector and attactched it to the loose black white wire from the switch it's likey that it will turn the gition off as it should.

Taking the black white wire from the switch to earth, wont.. that wire when the switch in the 'off' position is already going to ground! Its the one in the loom conector connected to the CDI that eeds to be earthed to kill sparks.
____________________
My Webby'Tef's-tQ, loads of stuff about my bikes, my Land-Rovers, and the stuff I do with them!
Current Bikes:'Honda VF1000F' ;'CB750F2N' ;'CB125TD ( 6 3 of em!)'; 'Montesa Cota 248'. Learner FAQ's:= 'U want to Ride a Motorbike! Where Do U start?'

stinkwheel · Bovine Proctologist Joined: 12 Jul 2004 Karma :

A simple horn button will do it. They earth to the handlebars. Simply connect that to the white on black. Push to stop.

In fairness, I'd want a kill switch on my bike anyway, even with a working ignition switch.
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I did the 2010 Round Britain Rally on my 350 Bullet. 89 landmarks, 3 months, 9,500 miles.

Tamsin · World Chat Champion Joined: 07 Mar 2014 Karma :

I'm pretty certain that its the original iggy switch, its definately a different (and definately the original) switch on my 2001 bike.

What I read from your post tef is that they *may* be a dangling wire somewhere around the engine connection block? I certainly didn't see one but will look again tomorrow.

Teflon-Mike · tl;dr Joined: 01 Jun 2010 Karma :

Tamsin · World Chat Champion Joined: 07 Mar 2014 Karma :

So would this be earthing the black/white wire to create a momentary short?

I have a handlebar mount on/off switch, I was going to just turn it into a switched earth for the CDI if I can't get it sorted out.

Everything is connected up correctly inside the headlight, including the black and white wire

Teflon-Mike · tl;dr Joined: 01 Jun 2010 Karma :

Tamsin · World Chat Champion Joined: 07 Mar 2014 Karma :

Now working on it again. Continuity at the switch is correct. When switch is off there is b&w/green continuity and when it's on its red/black continuity. B&w is in the connection block btw...

Tamsin · World Chat Champion Joined: 07 Mar 2014 Karma :

I found that the b&w wire wasn't connected to the cdi. Plugged it back in, now the damned thing won't start at all. Even if I take the wire out again

Tamsin · World Chat Champion Joined: 07 Mar 2014 Karma :

I'm not getting a spark... Sad

Tamsin · World Chat Champion Joined: 07 Mar 2014 Karma :

So it turns out the cdi earth wire came adrift when I sorted out the B&W wire. Which was why I wasn't getting a spark.

Bike is now running lovely and all that's left to do is headlight bulb replacement and diagnose why the rear light isn't illuminating.

Thanks for the help guysl