Hi All,  I have had my 125B since 1988 and have always had an issue when cold that it would die when you turned the handle bars one way.  I wiggled wires and it would pick up and run and not do it again.

Well, finally something gave out and it has no spark and won't crank with the starter.

I bought a new main wiring harness as the original had been chopped at a few times so seemed logical to fix what I knew was sketchy anyway.

New harness is in, more of the electrical is working (neutral indicator for example that never worked before) but still no cranking and no spark.  Lights work,   New battery, fully charged too.

The wiring from the right handlebar switch is red / white and blue / white.  Those plug right into the main wiring harness.  I have jumped those but don't get it to crank.  It seems like there should be more there but i can't figure out.  Somepne had another jumper wire in there but I can't figure out why.  It fell out when I was connecting wires and I can't figure out where it would have been.

I can short across the starter solenoid and it cranks, but still no spark.  

Anybody have a color wiring harness for this series?  

What am I missing?

Thanks.

Look in the service manual.   Just "jumping" wires randomly is not a great idea.  Yamaha wiring codes are kept pretty much the same and there are lots of diagrams in the manuals. 

Blue/White is for the starter switch.  Starter button connects blue/white to GROUND when you push the button and then the starter should crank...  if it's connected of course and the solenoid is good. You can touch the blue/white to a good ground and see if it cranks. 

Red/White powers the ignition coil.  It needs to be connected to a brown wire that comes from ignition switch.  Brown wire has 12 volts when ignition key is on.  Kill switch on handlebar connects red/white to brown when switch is in the "run" position.

When red/white is connected to battery power you should have spark. 

 

Without reading into it just yet, a favourite place for broken wires is at the steering head from contant flexing left-right.
Maybe a broken brown if spark stops .
Did they still have electricstart in "88, sounds late.
Could be a broken red if everything stops.

Sorry i see Mark say red/white powers the coil.

It looks like I am missing the brown wire from the right handlebar switch harness. There was some extra splices that I removed and now only have 2 wires coming from the right grip. I think If I can find the brown from the right side I should be in business.

Thanks for the help.