Motorcycle Repair: Honda CB750 K 1982 Electrical System, honda cb750, stator coil

Question
Hi Chris:

I have a 1982 Honda CB750K. I recently took it out for a short ride. After stopping, it would not re-start - battery dead. Solenoid clicked once when I hit the starter but not enough juice to turn it over. I boosted it to get it started - seemed fine. Half way home it died again at a light. Boosted again, but as soon as RPM dropped below 3000 failed to run. If I left the booster cable on (briefly) it would continue to run. So I assumed battery totally drained and charging system non-functioning. Trailered the sucker the rest of the way home.

Charged battery overnight. Bike starts fine. Battery reads 12.5V at rest. Battery reads 12.0V when running at idle. Increasing revs to 3000 - 5000 RPM only marginally increases output to maybe 12.1V. So system appears to be discharging when running.

Checked resistance (ohms)of three leads from stator and each have continuity with one another and no short against ground lead. Voltmeter shows only 4V from each of the leads while the bike is running. Would have thought it would be significantly higher.

That's pretty much the limit of my electrical system knowledge. Suggestions?

Thanks,

Keith  

Answer
Hi Keith.
 It is clear from the readings that you got, the stator coil is going on you.  You should be charging at 13-15VDC at the battery when the bike is running at idle.

Yes, you system is producing a charge, but not enough to charge the battery and run the rest of the electrical system (ignition, lights, signals, etc.).

Replace the stator coil and your problem will disappear.

Good luck.
FALCON