Motorcycle Repair: 1973 honda cb450, stator rotor, continuity check

Question
QUESTION: My 1973 cb450 is having electrical trouble. I put in a new battery in after I thought the battery was bad. It will run with no problems off the charger for a while but eventually the lights go out and almost stall out the bike if I try to use them. I assume the battery isn't getting charged. What should I check for and what do I fix? -Thanks Rick

ANSWER: Aaron, there are four parts to the charging system.  The stator, rotor, regulator and rectifier.  The stator can be checked with an ohm meter.  Check the resistance of the three yellow wires.  They should have about equal resistance between them and no continuity to ground.  You can check the rectifier with the VOM meter with the continuity check function. Don't use the ohm check function because it will register high resistance which will make you think it bad when it's not.  If you put the ground connection (black probe) on the center post of the rectifier and the red probe on the each of the three of the connectors on the rectifier input, it should show continuity one direction and no continuity when the leads are reversed. I've seen the magnets go bad on the rotor but if if it grabs a screwdriver and hold sit good, it's probably okay.  Lastly, the regulator could be bad but those can't be checked without special equipment but if the others check out okay, it's probably the regulator.

Before doing any of this, charge the battery, and check the voltage at the battery with the engine reved up to about 3-4000 rpm.  It should be 13.5 volts or higher.  Also make sure the brake lights aren't stuck on.  The alternator doesn't put out enough current to rund the brake light as well as all the other lights so if it's on, the battery will go dead after a while.

Regards
Rich



---------- FOLLOW-UP ----------

QUESTION: Rich,
Thanks for the help. I found that the wire coming off the rectifier going to the battery was corroded and broke off. Replaced it and problem solved. I'm now trying to upgrade the headlight to a xenon light system. The problem is the bulb and reflector are one unit. Do you know of any aftermarket reflectors that can be bought? The only thing that I can think of is to cut the bulb out except then it will probably just explode in my hands. Not good.

Answer
It may take a little while but you can probably find a later year bike that had the round head light and had a replaceable bulb.  I think the 78-80 750s had those type of headlights.  The problem will be that you'll have to use the larger headlight shell.  The early 450s had a smaller headlight than later years.  

Regards
Rich