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Motorcycle Repair/Testing charging alternator & rectifier


Hello Bill.Ihave cb77 1964 Ihave rebuilt bike but would like to get some exspert advice on testing Alternator and rectifier ihave a multi meter. Would be gratful for your help what would be a good book or manual which deals with electrics.  Thank you Albert.

I have a number of files covering Honda CB electrics as part of my CB72-77 Restoration guide data package, available on CD or Dropbox download. That's available from my site.

The system isn't complicated but has a few quirks to it.

Check links here for free downloads of Honda repair information

Wiring diagrams here:  

Retrobikes in WA offers nice OEM looking rectifiers that are silicone diode, instead of the old selenium versions, which help with charging system output. Make sure your stator coils are not loose on the mounting posts and the output wires show connected to each other but not to the stator frame (ground). If the coils are loose they can bounce around and short out the energy output to ground before it ever leaves the wire connectors.

If your rotor doesn't have an "L" after the CB72 stamping it is of higher output than the later L types. Rectifiers are a little more tricky, but basically they are just a lump of diodes, so check with your meter in one direction, note readings and then switch the leads from + to - and test each one the three connections again. Should be real low in one direction and very high resistance in the opposite direction.  A lot of people are using the little Radio Shack full-wave bridge rectifiers and mounting them on a heat sink/bracket. Cheap fix, but not pretty.

The headlight switch on the headlight shell turns the lights ON and also connects the brown and yellow stator leads together electrically to offset the voltage/current drop when the light bulbs are all lit up.

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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