Motorcycle Repair: CB 125 SE 1972, wire loom, spark generator


Question
Hey Rich
Have a cb125that I am about to resurrect can not get spark. Generator is putting out power. Main key is operating. Coil and condenser are ok. I have read that a battery is required to excite the magneto to get a spark. the black wire coming from the wire loom that connects to the coil I have checked with a meter and when I ground it to the motor I get a circuit to me very strange as this is where I though the power for the spark would come from. Maybe this is earthed because something else is not open in the wiring loom. The loom has not been messed with and is in relatively good condition.

Cheers Brenden

Answer
Brenden, the black and white wire to the coils is the power wire into the coils.  It should have 6 volts when the ignition key is turned on.  The yellow or blue wire going to the points is the ground coil circuit and the plug fires when the points open breaking the circuit. Make sure when the points are closed they are making a good ground.  You can check the points connectivity with a VOM.

Regards
Rich