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Honda TL125 to CB125S Engine swap......

Old's Cool - ADVrider -
Hi guys. Im a newby to the forum and live in UK.

Im after some advice if I may from some of the gurus here.

Apologies in advance for my first post being a cry for help!

I have a few bikes and last year added a 1976 Honda TL125S to the stable.....

A great little bike which one day I'll fully restore but at the moment the novelty of riding and enjoying it hasn't worn off yet!

One thing I have done tho is removed all the lights, indicators etc etc from it and made it a day-light only bike for the road/offroad.

I also reduced the wiring/ignition to purely a kill switch, coil, points and spark plug which was an easy job like this......

Earlier this year I bought and restored a CB125S engine from the same era, with a view to fitting it o the TL (its a direct swap) and then stripping the TL engine to give it some TLC.

Here's the CB lump......

I had hoped to carry out the minimalist wiring/ignition mods on this one and mistakenly thought it'd be the same as the TL as they're both 6V points engines which are almost identical.

I was wrong!

The CB125S wiring diagram is here.....

This diagram showns it has a reg/rec and three wires from the alternator.

No matter what Ive tried the most I can get from the CB engine is a very weak spark which isn't enough to get the thing running.

I fitted a reg/rec and also tried a battery (in case it was needed) and fitted new points and set timing but still no good. I am using the original TL coil.

So here I am, hoping someone may be able to lend some advice!!

Can any of the guys here who understand these things suggest a simplified diagram to show only the ignition system for the CB, similar to the minimalist dwg for the TL above, which an electrical-knowledge-lacking amateur like me could understand!?

Would be eternally grateful if you could!


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