1982 CB125 Superdream not getting any spark.

[msherry21]

Hi folks, my 1982 CB125 Superdream isn't getting a spark from either plug.

I've check and replaced spark plugs, spark plug caps and leads.

I've use a multimeter on both CDI's and they seem to be fine.

I've checked the coils and they also seem to be working.

I've checked the main earth cable from the starter motor and the earth strap from the engine to the battery, cleaned them and the mating surface.

Still no spark on either side, this also makes me think it isn't the coils or CDI as you would think one would at least work.

What other earths am I missing? I've been around the green earth wires that I can find to clean up etc.

When I try to start the bike, the starter does turn, the neutral light is on but I'm just not getting any spark.

Cheers, Michael.

[WD Forte]

Show us the bike Mike
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bikers smell of wee

[jaffa90]

Consider that some bikes have safety cut out switches that kill the spark only, as in clutch / side stand .

[Nobby the Bastard]

On an 82 superdream?
____________________
trevor saxe-coburg-gotha:"Remember this simple rule - scooters are for men who like to feel the breeze on their huge, flapping cunt lips."
Sprint ST 1050

[WD Forte]

Nope no clutch switch, it doesn't even have a killswitch
just switches on/off at the ignition switch.
Just looking at the wiring diagram.
Very simple system, was just wondering if it had been improved
with a seat hoop and brown cover.
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bikers smell of wee

[jaffa90]

Could be modified ?
https://www.motorcycleid.com/1982-honda-cb125-kill-switches/

[Nobby the Bastard]

[jaffa90]

"""I've checked the coils and they also seem to be working."""
Does that mean you have low tension pulse voltages to both coils when the engine is turning over?

[Nobby the Bastard]

The fact that there's no spark from two mostly independent circuits means you need to look at the bits that are common. Engine earths and power from the ignition to the pick up coils.
____________________
trevor saxe-coburg-gotha:"Remember this simple rule - scooters are for men who like to feel the breeze on their huge, flapping cunt lips."
Sprint ST 1050

[Nobby the Bastard]

[Robby]

Two CDIs? Are you sure? I would expect one CDI, 2 coils.

I don't know bike intimately, but I am very familiar with the CB250RS from the same time period. One trick for a no-spark situation is to unplug the alternator from the reg/rec. So follow the wires from the alternator, there should be two bundles. Pop out the connector with 3 yellow wires from the reg/rec.

Try starting the bike. If it suddenly works, the stator is failing. Don't take it for a long ride, it won't be charging the battery.

All of this is assuming that the superdream uses a self-exciting ignition system like the RS.

Of course it could also just be a broken earth wire somewhere. Lots to go wrong on a 40 year old bike.

[Nobby the Bastard]

I've found wiring diagrams with single and double points now....
____________________
trevor saxe-coburg-gotha:"Remember this simple rule - scooters are for men who like to feel the breeze on their huge, flapping cunt lips."
Sprint ST 1050

[WD Forte]

The diagram I have shows a typical AC CDI system similar to the CX
and probably other bikes of that era.

The stator sacrifices some sharge coil space for source coils which supply the AC power to the twin CDI units as the engine spins
Each CDI is triggered by its own pulser
The engine is stopped by shorting the source coil output to ground by contacts on the ignition switch which close when turned off.
The whole thing runs independantly of the bikes 12V system

If the bike is stock, it will only take minutes to do some simple tests
to see where the problem is.
If its been 'improved' cafebobberchoppered etc then fuck knows
that's why I asked for a pic.

Here's the diagram I have
https://imgur.com/vdjKBn3.jpg
____________________
bikers smell of wee

[Nobby the Bastard]

Ah, but the chances are it's powered by the normal charging system and is DC. AC doesn't play nicely with capacitors....

I'm also still confused with the whole twin CDI bit. It's an IL2 which means both pistons will fire at the same point on the crank so why not just use wasted spark?

(I'm ignoring things like the TL which has an offset crank to replicate the power strokes of a V2)
____________________
trevor saxe-coburg-gotha:"Remember this simple rule - scooters are for men who like to feel the breeze on their huge, flapping cunt lips."
Sprint ST 1050

[WD Forte]

The AC power is rectified as soon as gets into the CDI box
where it charges the dump cap

If Op has put 12v on the black/white wire
he's probably fooked the CDIs up.
they dont like it up em see? seen that before.
____________________
bikers smell of wee

[jaffa90]

Looks like the O.P. is still dreaming!