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SOHC.co.uk Forums => SOHC Singles & Twins => Topic started by: Craizeehair on July 11, 2025, 03:52:22 PM

Title: CB125K3 Condenser location and checking for spark
Post by: Craizeehair on July 11, 2025, 03:52:22 PM
Bit of a mouthful for a title!

I’m doing a little housekeeping and going through the boxes and bits I have for this bike, the coils are still fitted to the bike, it does look as though they may not be in the best shape though. There is no condencer on the bike or in the boxes, the parts list does show a condencer for this bike but the wiring diagram I have doesn’t show one on there.

I have a couple of questions that I hope you can help with.

Where does the condencer connect to, it has two wires to it but where do they connect… Apologies if this is basic stuff but I think I could work it out if I could see it on the wiring diagram?

Also, I do need to get a battery at some point but that’s not so easy as it seems that I can’t get one delivered these days.

Second question is, once I have a battery could I check for spark without a condencer, I’m not talking about firing the bike and running it, just checking for spark at the plugs?
Title: Re: CB125K3 Condenser location and checking for spark
Post by: Toko_Jo on July 11, 2025, 04:19:23 PM
You need a condenser fitted to get a decent spark. Condenser is wired across the points (and one side is ground).
Title: Re: CB125K3 Condenser location and checking for spark
Post by: taysidedragon on July 11, 2025, 04:29:26 PM
If the condenser is not mounted on the points plate I would expect it to be mounted separately somewhere between the points and the coil.
Follow the cables from the points and you should find it, possibly next to the coil.
On vehicle wiring diagrams it's commonly shown as 2 short, parallel lines at right angles to the wire.
Title: Re: CB125K3 Condenser location and checking for spark
Post by: Johnwebley on July 11, 2025, 04:41:03 PM
On my 200 twin,it only has one set of points, driven off the camshaft,

The condenser is connected to the points cable and mounted on the cylinder head,

As for the battery, I suggest the yellow brick Mottobatt gel,

Easily obtained from Tayne Batteries, no liquid, no problem



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Title: Re: CB125K3 Condenser location and checking for spark
Post by: Craizeehair on July 11, 2025, 04:59:04 PM
Thanks again!!! I’m a proper wally, it’s on the points plate, from the diagram it looked as though it was fitted by the coil so I hadn’t engaged my brain!
Title: Re: CB125K3 Condenser location and checking for spark
Post by: Craizeehair on July 11, 2025, 05:00:21 PM
As for the battery, I suggest the yellow brick Mottobatt gel,

Easily obtained from Tayne Batteries, no liquid, no problem



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Thanks for the battery suggestion. I shall check that out.
Title: Re: CB125K3 Condenser location and checking for spark
Post by: Craizeehair on July 11, 2025, 07:27:37 PM
Probably a(nother) dumb question but could I put a 12v battery on it, just to kick it over with the plugs out and grounded to see if there’s spark at the plugs? Would that cause any damage?
Title: Re: CB125K3 Condenser location and checking for spark
Post by: Bryanj on July 11, 2025, 09:59:11 PM
If its a 12v system no if a 6v yes
Title: Re: CB125K3 Condenser location and checking for spark
Post by: Craizeehair on July 11, 2025, 10:02:40 PM
Presumed that would be the case, it’s 6v so was hoping just that would be ok just to check spark with the kickstart but I’m not in that much of a hurry to do any damage.
Title: Re: CB125K3 Condenser location and checking for spark
Post by: Bryanj on July 11, 2025, 11:07:49 PM
Same resistance but double voltage equals double current which strains insulation, ok for a horn which is only on for a second but not a coil
Title: Re: CB125K3 Condenser location and checking for spark
Post by: Johnwebley on July 12, 2025, 12:03:27 PM
If you're not sure of the voltage,

Check a few bulbs

Should be marked 6v or 12v



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