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Motorcycle Repair/ct200 Overcharging?


Hi Bill -- Thanks a million for your time.  I have recently restored a '66 CT200.  Everything's working and fine, except that while upgrading the rectifier with the Radio Shack unit, as was suggested by several 'CT' sites, I noticed that my system is putting out 8.4 volts @ 3,000 RPM.  Questioning this reading, I put the old rectifier back on for a 'base' check.  It was the same.  Battery is new.  Is this alright, or will it burn my bulbs out? Thanks again!


I had to use the C200 wiring diagram for a reference, although the CT200 should be similar and also like the early CT90s.

With two different rectifiers doing the same thing, either you have some wiring connection issues or that is the way it is for that charging system. A fully charged 6v battery is really supposed to show about 6.4v on a quality volt meter. The charging systems will send out more than that under full output conditions. Make sure that the "new" battery is fully charged on a charger and that it load-tests okay.

You didn't mention whether the reading was with lights ON or OFF. When the lights are off, you are feeding the rectifier with the two legs of the three coming from the stator. When the lights go ON, then the yellow and white wires are connected together at the ignition switch, sending the extra voltage/current to the rectifier to offset the lighting load. Both readings should be about the same, all things being equal and correctly functioning.

Check your wiring connections in the headlight shell to be sure that all colors match up correctly. All ground connections need to be clean and tight, including the battery and rectifier grounds.

Bill Silver

Motorcycle Repair

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Bill Silver


Need help with vintage Hondas from the 1960s? I am an expert with 250-305cc bikes in particular and most all of the other pre-91 models, in general. I do NOT claim to have a great deal of experience on Gold Wings, Cruisers, ATC/ATVs and dirt bikes.


I have owned/ridden/maintained Honda motorcycles for 35 years. I have written five books on Honda repairs and collecting. I was a service manager for two Honda shops back in the 1980s.

VJMC (Vintage Japanese Motorcycle Club) of North America

VJMC newsletter, as editor for two years and as contributing editor currently.

3 years auto shop in high school, teacher's aide in Automotive Technology in Jr. College, Diesel mechanic course in college, self-taught mechanic and automotive writer.

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