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Motorcycle Repair/Honda C100 wiring follow-up


Hi, Wayne,
I just wanted to follow up on the info you gave me last night to see if I wired my motorbike correctly.  Re: the rectifier    What I did was plug the red male plug and the red female plug from the rect. into the double socket/plug of red wires. From the double socket/plug a red wire goes to the fuse and a red wire goes to the wiring harness. It looks like this:

red from harness to socket/plug  red to rectifier
red from fuse    to socket/plug  red to rectifier
white wire from rectifier to the wiring harness

Re: Brake switch(B.S.)  I ran the green w/yellow wire from the B.S. to the green wire that goes to the tail/stop light and the black wire from the B.S. to the black wire to the key switch which also connects to the black w/ green wire that goes to the main coil.

Does this seem to be correct?  I didn't try to start the engine or turn on the key for fear that I didn't have it sorted correctly
Thank you so much for your information and patience with me.

Hi Al,

These sound okay to me:

red from harness to socket/plug  red to rectifier
red from fuse    to socket/plug  red to rectifier
white wire from rectifier to the wiring harness

The brake switch I am not sure on as well as the coil wiring.

The ignition coil generally has a black wire that goes to the points
and the ignition switch. The points operate normally
with the switch on and then with switch off the switch just
grounds out the coil wire to stop the engine.

The other ignition coil wire runs to the engine case into the flywheel
coils where the ignition coil gets it's power from.

Connecting your brake light to this would not be great
as this power is not as steady as actual battery power.

The brake can connect to any live battery wire like the red
and then the other brake switch wire goes to the brake light.
Check your brake light by connecting the battery to it
separately to make sure it works.

The best wire for the brake power will be one that is live with the
ignition switch on and off when the switch is off.
You can check for this with a test light or multimeter.

There is also a possibility some wires may be different
than usual depending on where the bike came from,
what was done on it since new.

Some Hondas used a battery ignition but yours should
be just a magneto system so the ignition coil would
only have power when the engine is turning over
so not good for the brake light which needs steady
battery power.

I am not sure if you have this wiring diagram:

Let me know if you need to know how to check something in particular
or if anything looks much different than the diagram above.

I think most of it looks right but better to be safe than sorry.
You can try a quick connect of the battery and
as long as you have a fuse it should be okay.

I have a CT90 in pretty good shape but it uses a battery ignition
which dies when the battery is low.


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Wayne S.


Licensed Motorcycle Mechanic, Knowledge of motorcycles from 1960 up, Japanese, British and most other brand motorcycle repairs.


Worked for Yamaha, Honda, Suzuki, Kawasaki British: Triumph, Norton, BSA Other: Most Scooters and Mo-Peds

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