Serious Charging Problem

[adorji11]

i recently took my 81 honda cb650 to the shop to have a look at the charging system. the battery is brand new so i know thats not the problem. they said the rotor was faulty and that they could take it to an alternator/engine rebuild shop. however, the rebuild shop said it was fine. The shop swears up and down that the rotor is the problem but i dont want to buy a used rotor for it not to be the problem. any thoughts or suggestions would be greatly appreciated. thank you, Ayang.

[onepieceatatime]

You will need an ohmmeter.
Rotor resistance should be 4-10 Ohms between sliprings, no contact to ground.
Stator resistance should be 0.4-0.5 Ohms, between each pair of yellow wires, no contact to ground.

Usually it is the rotor that fails on these bikes, and once failed takes out the rectifier/regulator.

[Volker_P]

Welcome here!

Yes, most probably rotor. In some tricky cases, the rotor fails when hot or/and in rotation, so you can't detect it by the slipring measurement above.

Nevertheless worth checking all charging related cables and contacts.

The RR may survive a rotor failure or not. On page 16-8 of the manual linked below there is a description of a load/performance test for the RR.

[marke]

^ Volker - you should make a youtube video of you checking a rotor... Since everyone who visits the site asks how to do it (myself included).

[cb650]

Someone did a video. Dont remember if it was here or on sohc4 though. Was on a dohc750 but its the same parts.
Found it.
http://www.youtube.com/watch?v=2oIFZofcqXY
Here is the thread from sohc4.
http://forums.sohc4.net/index.php?topic=110322.0

[Volker_P]

Thanks!
Much easier for me to swap valve stem seals than making a youtube video!

[M_Hills]

You will need an ohmmeter.
Rotor resistance should be 4-10 Ohms between sliprings, no contact to ground.
Stator resistance should be 0.4-0.5 Ohms, between each pair of yellow wires, no contact to ground.

Usually it is the rotor that fails on these bikes, and once failed takes out the rectifier/regulator.

I am doing these same tests on my bike and want to be sure that I am not screwing it up...
When you say "no contact to ground" does that mean ground anywhere on the bike or is there a specific "ground" per specific scenario?

[onepieceatatime]

You will need an ohmmeter.
Rotor resistance should be 4-10 Ohms between sliprings, no contact to ground.
Stator resistance should be 0.4-0.5 Ohms, between each pair of yellow wires, no contact to ground.

Usually it is the rotor that fails on these bikes, and once failed takes out the rectifier/regulator.

I am doing these same tests on my bike and want to be sure that I am not screwing it up...
When you say "no contact to ground" does that mean ground anywhere on the bike or is there a specific "ground" per specific scenario?

There should be no contact to ground anywhere on the bike, or if the rotor is off the bike, no contact to the body of the rotor as it will be grounded through the engine when mounted on the bike.