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Motorcycle Repair/honda 125xl electrical system


rectifier is good but no charging .why?.

Omon, How did you test the rectifier?  With an ohm meter or checking voltage in and out of the rectifier?

The rectifier must receive voltage from the stator windings...  only two are active when the bike is running with the lights OFF. When the lights are turned ON, the headlight switch connects the extra leg of the stator to the rectifier leads for additional voltage/current.

The battery must be able to take a full charge and a load test. If that passes, then you have to check the stator windings for continuity to each other, but not to ground. Test for AC voltage going to the rectifier and DC coming out.

If you have extra lights or non-standard bulbs in the circuit it might be more than the system can provide. The charging system is designed to maintain a fully charged battery under normal conditions, but it won't charge a dead/dying one. Check to be sure that the brake light switch is not staying ON when you are riding the bike, as that extra draw can pull the battery down in a hurry.  use the XL100 diagram for reference.

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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