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'82 GS550L Alternator Rotor Interchange

  • Thread starter Thread starter xcutnr
  • Start date Start date
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xcutnr

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I just got the high output stator and a R/R from electrex. Now the alternator is putting out a max of about 55 VAC on each leg. The Rotor is pretty much all that's left, right?

I'm trying to find something a little cheaper since I just dropped $250 for a new stator and R/R. I need to know what bikes this will interchange with. I'm looking at '82 GS550ES, which I figured would, an '81 GS450, which looks about right, a '77 GS550, which doesn't really look right. Any other suggestions, or does anyone have one that will work? Thanks.
 
First check it with the stator wires disconnected &
use a different meter You AC scale could be bad
 
Re: '82 GS550L Alternator Rotor Interchange

xcutnr said:
I just got the high output stator and a R/R from electrex. Now the alternator is putting out a max of about 55 VAC on each leg. The Rotor is pretty much all that's left, right?...
Click to expand...

The rotor is not nomally a replacement item, as it is just a powerful permanent magnet on the end of a shaft. Other than rotation, there are no moving parts and no wear since there is an air gap between the rotor and the stator.

The 55 VAC reading doesn't mean that the replacement stator is bad. In fact, when all three legs are putting out the same voltage this usually means that the stator is OK. The disconnected stator wire voltage should be checked at 5,000 rpm. Did you test it at this engine speed?

In the final analysis, the output of a charging system is best tested while it is operational. To perform a proper test, your charging system wiring should be inspected and cleaned of all corrosion and poor contacts. Your battery should be new or in excellent condition. Use a digital multimeter to make measurements. When everything is connected, what is your battery charging voltage at 5,000 rpm?

If the charging system is operating properly, test load capacity could be checked by an incremental increase of loads to the battery to the point where an equilibrium is reached, i.e., the battery will no longer charge or discharge under the full electrical test load. To compare a standard with a high output stator, the same test would have to be run with both components to confirm a difference in test load capacity.
 
Here are my thoughts for what they are worth.

A 'high output' generator usually means providing more output current capacity than standard. The only safe way to do this is use bigger wire in order to reduce resistive losses (heat) due to the larger current. Bigger wire wound on a bobbin similar to the standard stator means fewer turns, consequently a lower voltage, both loaded and unloaded. This isn't all bad, since the regulator/rectifier will have less heat generation as long as the loaded voltage is high enough to allow charging.

As above, you really need to know the loaded voltage to see if the stator is developing enough voltage and current to allow charging. Unloaded voltage only tells you that the the windings are not open and that they are not shorted (melted from supplying too much current at some point in time). It is a diagnostic method used to check the windings, not to measure capacity. Since they are all the same, I would expect them to be ok.

If you are really into checking it, my recommendation is to go purchase a cheap ammeter at an auto parts store and use jumpers (must be big wire) to connect it between the output of the regulator/rectifier and the battery. Then make sure everything that can be turned on is turned on i.e., headlight, brake light, turn signal, etc. and see how much current is being supplied. You also need to measure the voltage across the battery at this stage to make sure it is about between 13.6 and 14.6 volts. This will tell you if the charging system will carry your load.

My father used to have a string of auto headlights he could add one at a time across the battery to see how much current a tractor generator could supply before the voltage dropped. If you do something like that, be careful since you could burn out your rect/reg and/or stator.
 
Ok, here's the problem: all the wires are new, since I just replaced the R/R and stator. The battery is brand new and fully charged. I tested with stator wires disconnected, engine at 5k. All 3 legs give about 55VAC. I believe the stator is fine. The old stator was burned up (shorted), and when checked gave no voltage. But if the rotor was good, that should be all that's needed to produce the AC voltage, right? Anyway, with the R/R plugged into the stator wires, I get 7 volts charging with the battery disconnected. I only have one positive wire. Now what? I've been told by some people that this rotor is a permanent magnet that cannot lose it's magnetism, and by others that it can, and that just one of the magnets could be bad, leading to the low charge. My manual says nothing about it except that it usually doesn't need replaced unless the bike is in a wreck.

At any rate, if I do need a new rotor, I need to know what will work before I miss out.

Anyone have any other ideas?
 
xcutnr said:
Anyway, with the R/R plugged into the stator wires, I get 7 volts charging with the battery disconnected. I only have one positive wire. Now what?
Click to expand...

What do you mean :?: Are you testing the output from the R/R without the hot lead connected to the battery circuit? If so, this is not a proper test, and I'm not sure why you are doing it. :? Charge the battery first, and connect the R/R hot (voltage output) wire to its normal connection. Start it up and check the battery voltage at 5,000 rpm.

I've been told by some people that this rotor is a permanent magnet that cannot lose it's magnetism, and by others that it can, and that just one of the magnets could be bad, leading to the low charge. My manual says nothing about it except that it usually doesn't need replaced unless the bike is in a wreck.

At any rate, if I do need a new rotor, I need to know what will work before I miss out.

Anyone have any other ideas?
Click to expand...

You don't need a new rotor. Follow the normal troubleshooting procedures to determine if there is a problem. Sometimes, even a new R/R can be bad like any other electrical component. I think that your stator is OK, and probably the R/R too. Test the system with everthing connected and let us know the results.
 
No, I've got a fully charged battery, and with everything else connected, when I disconnect the battery, even at 5k, I only get about 7 volts. With the battery connected, it starts at over 12 volts, and slowly drops the longer it runs. When I run the charts, it comes up that the stator is bad.
 
You shouldn't disconnect the R/R connection to the battery to test charging while the engine is running.

If you are using an accurate digital multitester and the battery (connected) is not reading in the 13.8-14.5V range @5,000 rpm, then the R/R may be defective.

If the stator has already produced 55VAC @5,000 rpm, this would indicate that it has passed OK. The only other test for the stator is a test for shorts or opens with the engine off. But, if it were to fail that test it wouldn't likely produce the 55VAC that you are getting with the engine running.

What test in the chart do you refer to when you say that the stator is bad?
 
Measuring the voltage output of the R/R with the battery disconnected won't tell you anything. You must have the battery (or a load of some kind like a physically big resistor to ground) to have a complete circuit.

Are you sure the R/R has a GOOD ground connection? I finally figured out on mine that the ground lead had broken right before the crimped on connector and replacing the connector fixed it. Don't assume the bolts that attach the R/R to the bike are grounded either, mine weren't!
 
the only way to hurt a rotor or any permanent magnet is to A break it or B expose to sustained EXTREME heat.
 
Another question, in order to check your multimeter. Have you tried measuring other batteries, like on your auto to see what the standing voltage is with the auto off and then with it on? Does it read 12.6 - 13.0 when standing and 13.6 - 14.6 when running?
 
The meter is fine. According to the charts, I should have over 80 VAC from the stator at 5k with everything else disconnected. Since it's only 55 VAC, doesn't that mean the stator is bad according to the charts? I don't think it really is. I've read where some people said one of the magnets in the rotor could be bad, and it would cause lower voltage. The main ground and ground to the regulator are both good. The old stator was burned up. It looked like it had grounded out. The old R/R is probably still good, but I replaced it since electrex told me that it would burn up if I was using the high output stator. I'll try hooking it back up and see what happens, but the 55 VAC still bothers me.
 
The 80 VAC rating is for the stock stator. As jimg has pointed out, the wire size and method of rewinding the stator will affect the output voltage. A larger wire size might result in lower voltage if fewer turns are used, but the heat losses and voltage drop from the smaller wire size would be reduced. So, the 55 VAC output may be providing higher current under load that the stock 80 VAC output.

Electosport's own troubleshooting chart (which is better than the one on this site) specifies a minimum 50 VAC output. Since their chart covers all makes of motorcycles, I would assume that the 50 VAC covers an expected output from their stators. If you go to Electrosport Fault Finding, you can download their PDF Fault Finding Chart. I hope that reading 50 VAC in the Fault Finding Chart will make you feel better. :)

I would be concerned that you may have damaged the new R/R by running it at 5,000 rpm disconnected from the battery. If Electrex has warned you not to do so, don't hook up the old R/R and risk burning it up also. If the new R/R fails the test, contact Electrex and get a replacement under the one year warranty.
 
D.i.y R/r For Gs550

D.i.y R/r For Gs550

YOU CAN MAKE A R/R .THE SCHEMATIC IS VERY EASY.
IF YOU ARE INTERESTING SEND ME AN E-MAIL AND I REPLY WITH
THE SCHEMATIC. :-D

xcutnr said:
I just got the high output stator and a R/R from electrex. Now the alternator is putting out a max of about 55 VAC on each leg. The Rotor is pretty much all that's left, right?

I'm trying to find something a little cheaper since I just dropped $250 for a new stator and R/R. I need to know what bikes this will interchange with. I'm looking at '82 GS550ES, which I figured would, an '81 GS450, which looks about right, a '77 GS550, which doesn't really look right. Any other suggestions, or does anyone have one that will work? Thanks.
Click to expand...
 
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