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Motorcycle Repair/Rectifier/Regulator


Is it possible for the rectifier/regulator on a 2000 Yamaha V-Star 1100 to still not charge the battery even if the diodes check out as good?

Hello Jose,

The regulator/rectifier, as it's name supposes, has two separate circuits.
Even if you manage to check the rectifier's diodes, you can't check the regulator without professional equipment. A shorted regulator results low output to the battery.
To cut a long story short, yes, it is possible the diodes be OK but still no charge.

To be sure though that the problem is in the reg/rect, you must check the alternator output.
Locate the three white wires coming out from the left engine cover (flywheel) disconnect them from the main harness and measure the voltage (on the engine side!).
To do that, you will need a multimeter, capable to measure at least 100V-AC.
Measurement is taken between two white wires thus three measurements, a-b, a-c, b-c, if we "name" the wires abc. Polarity doesn't matter since it's AC voltage.

The results should be at least 19-20VAC at idle at every pair of wires, and more than 50VAC at 4000rpm. If these measurements are OK and you have less than 14VDC at the battery at 2000rpm,
then most likely the reg/rect is bad.

Best of luck.
Kind Regards,

P.S.: Don't hesitate to come back to me any time for further assistance.

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Lazaros Ampatzidis


I can help you on EVERY issue involving POST-1980 Japanese Motorcycles plus KTM and Husaberg. My field of expertise includes Engine, Transmission, Fuel system (carburation & EFI),Electrics and Electronics. Maintenance, repair and tuning. Road and off-road suspension tuning. Please don't ask me about non-Japanese Motorcycle, especially American built on which I have low to zero experience.


I'm a rider and hobbyist since childhood. 25 years motorcycle workshop mechanic.15 years motorcycle racing mechanic. In order of experience high to low:Kawasaki,Suzuki,Honda,Yamaha,KTM,Husaberg.

Hellenic (Greek) Technical School.Internal Combustion Engines Engineer. Automotive Electronics.

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