Motorcycle Repair: CB900 C 1982, honda cb900 custom, 1982 honda cb900

Question
Hi Bill,

I bought a 1982 Honda CB900 Custom. The bike was not charging and I
suspected that the rectifier was the problem. I replaced the rectifier and
instantly it started to charge 13.5/14 volts. But after one or two rides it did
not charge anymore. I bought a stator suspecting it was the problem but
readings of both are the same. Again, the new rectifier seems not to be
working fine as the resistance values are unreadable. Full resistance (=1) in
one  direction and no readings of the ohmeter the opposite way.
The rotor measures 1.5 ohms between slips (it should be 3.6-4.4 ohms).
It might be possible that the rotor is the problem and is smoking every
rectifier I put? Is the circuit so sensitive that 2 ohms difference will kill the
regulator/rectifier so fast?

Can you help?

Thanks,
Gabriel  

Answer
http://www.electrosport.com/technical-resources/library/diagnosis/fault-finding-...

http://www.electrosport.com/technical-resources/library/known-issues/street_4550...

Replace the rotor and all should be well, if the other components haven't gone up in flames with the main cause.

Rotors often change resistance values a lot when Hot vs Cold readings.
Unfortunately, a very common problem with vintage Honda fours of that era.

Bill Silver