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Discussion Starter #1 (Edited)
Hi, '75 CB 125 B6 Twin 12 volt coversion need some help - as the title suggests, my bike won't start after a 12v conversion.

Previous thread before the conversion: " 1975 CB 125 B6 Twin 12 volt coversion "

The following things were installed:

12v 6.5A gel battey
cl/cb175 stator
Reg/rect form Spark Moto
15a main fuse
12v bulbs

The stator and the reg/rect plugged right in. There only were 2 unexpected details:

1). There was a black wire standing alone (outside the plug) on the reg/rectifier. I read that this black wire connects to switched power so I hooked it up to a black wire in the wiring harness (with power only with ignition on). Is this right? or is there a specific place to hook this in?

2). The stator appeared to be identical to the one that came out of the bike except for slightly raised rings around the 6 mounting holes (the face of the stator ring on the original was completely flat around the mounting holes). Is this a problem?

While trying to start the bike the black wire from the reg/rect came loose from the wiring harness and the 6V coil pack started to melt with what looked like wax drops on the floor. Not sure if these events are related? Would the 6V coil have melted anyway?
I'm still getting spark from both plugs though. I've also got the point set to fire right on the F mark.


I have tried to follow the steps that others have taken but the bike won't come to life. Am I missing something?

Some additional questions:

1). How many turns out should I start off with with the idle and air mix screws on the carbs?

2). What should be the resistance measured in ohms for the coil pack (measured in the plug caps and also the 2 wires going to the coil)?

3). Do I need to upgrade the starter solenoid?

4). If the coil needs replacing, what would be a good 12v alternative that would fit onto the mounting holes and under the gas tank?

Any help would be hugely appreciated.
 

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This has been done a few times. There are some small twins experts around here who will be along but responses are sometimes slow on weekends so be patient.
 

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Sounds like you melted your coil. I did the same thing after converting my cb125. I had left the key on by accident and i don't think the old stock 6v could take it. I looked around for single 12v coils and found some results on Amazon but decided not to go that route since the mounting brackets probably wouldn't line up. I got an aftermarket 6v coil and attempted to wire in a 12v to 6v ballast resistor to step down the current before going into the coil. That didn't seem to work either so I'm just running the 12v set up with a new 6v coil. I'm extra careful not to leave the coil charging. No problems so far.
 

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Discussion Starter #4
Thanks for weighing in guys, I appreciate it!

Did some resistance readings today:

Stator:

A to B = 0.6
A to C = 1.4
B to C = 2.0

It is my understanding that these results should be similar - Does this mean that the stator is faulty? On further note - I checked all 3 leads to ground and none of them showed any value. So that's good?
On further note: I got identical readings from another stator (which I thought was faulty). On this other one I got some values when testing to ground. So that's bad? Was it a coincidence that these 2 stators showed identical values - or are they both faulty?

Coil Pack:

Primary side: 1.4
Both spark plug caps: 25.5

Is the value on the primary side a little high? Or is the part still working even though it started to melt?
 

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Discussion Starter #6

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On the 175, the condenser mounts onto one of the cylinder head stud / nuts.

However, no reason why you couldn't mount the condenser onto one of the bolts holding the coil onto the frame. In fact, I did just that, when I fitted that aftermarket coil onto my K4 175. I've since removed it, as I fitted electronic ignition, condenser not required.

One thing to be aware of with the aftermarket coil. The mounting studs are slightly closer together than stock, so you need to make up a small bracket if to wish to use existing holes in frame as mounting points. Alternative is to drill another hole in the frame.

As my bike is handily parked outside the back door with the fuel tank off, I'll try and take a photo.

20180807_083621.jpg

Other thing to be aware of, check the polarity, marked + and - on the end of the coil, wire colours don't match Honda.
 
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