[amritc]

Greetings everybody.
I have seen the charge from my AC/DC (4-wire) alternator drop to 22V on idle. Upon opening up the clutch case to check the alternator I note that the magnet has hardly any strength - I mean it barely pulls a piece of metal towards it. My question is whether these magnets are supposed to be like this? Or is it time to replace it...

[ERC]

22v is a lot of voltage is that what's coming out of your regulator?  ERC

[JVS]

How did you measure this voltage? Was it line to line straight at the alternator?

Assuming 22 volts is line-to-line, your idle per-phase voltage is 12.7 volts. I'm not sure whether the voltage with the bike on idle should be around 12.7 or 13-13.9 at the battery. In cars it's supposed to be in the latter range, so that will indicate that your alternator might need replacement...soon. But 12.7 on idle should be okay, and as Scottie J has mentioned below, if you rev the engine it should go over 12.7 per phase or around 23-23.9V line to line.

[mrunderhill1975a]

My magnet will pull the rotor nut with one or two lbs of force. What voltage do you have at the battery when revved ?

[AgentX]

Unscientifically, my rotor makes me think "goddamn, that's a strong magnet!"

[High On Octane]

We need some more information if we are to help you diagnose your problem.  If you have 22 volts at the battery, it would probably explode.  22 volts at the stator wires at idle seems fairly normal to me.  22 volts at the stator while revving would probably be reason for concern.  Did you test the rectifier?  Did you test the multiple phases on the stator?  Have you had the battery professionally tested?  Did you test the "magnet strength" with the alternator off on the edge face of the rotor or did you just try sticking a screw to the front face of the rotor?  You can't just 2 wires and decide it's a problem or not.  You need to test ALL the wires in the charging circuit and determine where the problem is coming from.

Scottie

[Vince]

     You are worrying WAY too much. If you rev the bike over 2500 RPM and there is 13.5+/- volts DC at the battery everything is fine. There is no test or published standard for how much magnetism the rotor should have. In 40 years of repairing bikes I have NEVER replaced a rotor for a magnetism issue. I have replaced rotors that people damaged with incorrect pullers, or physical damage from a crash. On rare occasion improper manufacturing has caused a physical failure.
     A charging issue on an RE involves the regulator/rectifier assembly, or the stator and the reg/rect. If the bike is charging you might ensure the connections are clean and tight and the primary oil is clean to help minimize future issues. If it is not charging then you must properly diagnose the issue by following the test procedures in the manual.

[amritc]

Ok thanks for that.

Just to clarify;

The 22V AC voltage is across the two purple wires straight from the alternator.
There is zero voltage across the yellow and orange wires - again straight from the alternator.

When revved to 2000rpm plus the voltage across the two purple wires grows to about 32-35V AC. The yellow and orange wires still show no voltage.

Voltage across the battery terminals is 12.27V DC without engine running. With the engine running the voltage rises to 12.6V DC. The battery is brand new (just replaced 2 months ago)

The reason I chanced upon this was due to the Headlight not switching on. My Headlight used to run on AC, this is powered by the yellow/orange wires from the alternator via the AC relay. I think the charging is too less given the ammeter shows significant discharge when braking or using the indicators or headlight (I moved the headlight direct to DC)

Any words of wisdom are, as always most appreciated.
Thanks again

[Blltrdr]

I would say that your problems exist because of your rewiring. The stock alternator barely supplies enough wattage, especially the kick start model. Someone on the forum has rewired their stock alternator to run DC only. You might want to search for that info. I'm positive some changes to the wiring for the headlight switch have to be made to run DC only system. Lowering your RPM's by activating your brakes with the headlight and taillight already on the activation of the stoplight will definitely swing your ammeter to the negative side (also add an occasional turn signal). You will definitely need to rethink a DC only system.

[barenekd]

The magnet can be remagnetized at any good auto electrical shop. I'm sure there are other places that can do it, too. This is actually a fairly common problem with these rotors. They just go away after awhile. Working in a shop in the old days, I found a few bad ones. They were recharged.
Bare 

[amritc]

hi, I have not re-wired the bike to DC only.

My headlight wasn't working via the AC orange/yellow wires from the alternator that go into the AC relay and then to the headlight. Thus I put in a direct DC supply only to the headlight and it works now.

[AgentX]

What may have happened is that you're no longer using the power made by the portion of the alternator coils dedicated to AC.  Thus there's a major inadequacy in the DC power being produced to run both the bike and the previously-AC lighting system.

To run the 4-wire alternator to a full DC-only system, you need to pair the wires to your DC rectifier AC input leads.  There is a way that works, and a way that doesn't...the right wires need to be paired to get everything in phase.

You may have a bad AC regulator which caused the problems with your AC wiring.

My guesses, anyhow.

[Blltrdr]

hi, I have not re-wired the bike to DC only.

My headlight wasn't working via the AC orange/yellow wires from the alternator that go into the AC relay and then to the headlight. Thus I put in a direct DC supply only to the headlight and it works now.

My point was you rewired to run your headlight on DC. As Agent X and myself have pointed out to you is that you are drawing to many watts for the system to work properly. As I pointed out, you can search the forum for the right way to rewire the alternator leads for DC only operation.

[High On Octane]

If you're only getting voltage from 2 of the 4 wires, I'd say one of the phases burnt out on your stator/alternator.  It is possible, as mentioned, that the regulator took a shit and then took out the alternator.  Watch these 2 videos, retest your bike and let us know what you find out.

Rectifier Diode Test
https://www.youtube.com/watch?v=kDx3zgOLShY

Stator Test
https://www.youtube.com/watch?v=5v2LtHlvcqI

Scottie

[AgentX]

If you're only getting voltage from 2 of the 4 wires, I'd say one of the phases burnt out on your stator/alternator.  It is possible, as mentioned, that the regulator took a shit and then took out the alternator.  Watch these 2 videos, retest your bike and let us know what you find out.

Rectifier Diode Test
https://www.youtube.com/watch?v=kDx3zgOLShY

Stator Test
https://www.youtube.com/watch?v=5v2LtHlvcqI

Scottie

I still guess the AC regulator went bad.  More likely than the stator taking a dump.  But I guess if the wires direct off the alternator show nothing, that would prove the unlikley case to be the true case.