Topic: Stator Failure Symptoms?

[B.O.X.N.I.F.E.]

Is stator failure on these bikes generally complete or will they continue to have some output as they fail?

Coming home last night the lights dimmed to almost nothing and throwing on the hi-beams killed the bike. It also seemed to be running a little weak. Charged my battery, replaced my rectifier with a known good unit, and got the same today. Non running voltage of the battery was around 12.2, about 8 - 9 volts at around 4k rpms.

What I don't understand was that the bike would die at stop lights, but with the headlight off I was able to kick it over and ride home fine.

[TwoTired]

It's pretty rare that stators fail unless wailed on with and axe or aggressive contact with bits of roadway.

The field coil or the connections to it are a far more likely culprit.
The field coil makes the magnetic field, the stator need this magnetic field to produce an output.

The 550 alternator, even when new, didn't make more power at idle than the bike uses, especially with the headlight on.

Lights on, the stock bike uses about 120 watts.  While at idle the alternator only makes about 40-50 watts.  This causes the battery to drop voltage, which the ignition needs to make spark.
Dropping off the lighting load, allows the battery to provide more voltage to the ignition circuit, and spark returns.

You'll need to test the filed coil resistance.  The 550 measures 4.9Ω, as well as all the connections within the charging circuit and the connections to the battery.

Also, the filed coil uses power power to make a magnetic field.  If the Black wire to the regulator has low voltage, it is this same voltage that makes the magnetic field.  Low voltage means a weak filed, and weak stator output.

You, are going to have to make meter reading for the system to find what is wrong.  Or, replace each part of it bit by bit until it works again.

This all assumes your bike is unmodified from stock, of course, information you left out of you post/query.

Cheers,

[DYSKORD]

My buddies 350four was having the exact same issue two months ago. Bought a new rectifier, problem solved. We went for a ride last night and when he opened her up it started bogging out, turned his headlight on and the bike completely died. We could kick start her but no electric start and she would die if the headlights were turned on. Pulled the side cover and the rectifier was unplugged. Plugged it back in, problem solved. So from my experiences with rectifiers failing and becoming unplugged to answer your question a failing(ed) rectifier sounds like your problem and would be my starting point.

[DYSKORD]

Twotired might be able to correct me but the rectifier converts the charge put out by the stator from Ac to Dc. If the rectifier is not doing its job then the charge put out by the stator is useless. Hence it would seem that the stator is not working but actually the rectifier is not converting the charge to a "useful" charge.

Hope this helps.

[TwoTired]

Certainly all six diodes in the rectifier need to do their job to get full power out of the stator.

But, the OP said he replaced his with a known good device and still has a problem.

FYI, the stator just won't make any or full power unless the field coil makes a good strong magnetic field.  Make sure White and green to the field coil get full battery voltage if you want max output from the stator.

Cheers,

[bryanj]

What about the regulator, its seperate from the rectifier

[B.O.X.N.I.F.E.]

What about the regulator, its seperate from the rectifier

Didn't know that'd be a possible culprit for a non-charging battery. I have an electronic unit from a porsche in there now. I thought it'd be a more reliable upgrade.

[TwoTired]

The "voltage regulator" is what supplies power to the alternator field coil.  If the Vreg fails to do this, the alternator makes no power.

[dave500]

you might find an alternator check list with specs in the faq?also trace any and all wires to do with the charging circuit and make sure the conectors are clean and tight,its best to unplug,clean,then replug them all,this might be your fix,also if the battery is getting old it might be time to get a new one,i think three years isnt bad for a little bike one.,if its dodgy itll affect the charging overall aswell.

[trueblue]

When I got my 650 it wasn't charging, in the end, after much cursing, swearing and head scratching, it turned out that my rotor was knackered and was drawing too much current through the reg/rec unit and had fried it.

[B.O.X.N.I.F.E.]

Last night I ran it and noticed, when I killed the headlight on the highway just to see what happened, that my neutral light and oil light are glowing faintly all the time. The neutral light has always done this when I ride in the rain. Is it an indicator of the possible problem?

The bike is pretty well sorted, I've gone through the entire harness and cleaned every connection, but that was 15k miles and two cross country trips ago.

[B.O.X.N.I.F.E.]

where you at twotired!

[AshimotoK0]

Back in the early 80's I have two stators fail on a 400/4's I used in the UK as daily riders. the fault on both  was that the magnet winding wire insulation broke down and shorted to earth. There should be no resistance between any of the three yellow wires and the mag frame. You can test this with a battery and bulb as a rough check. The alternator runs dry on the 400/4 but on the 750 runs in oil and I have not seen this type of failure on my limited experiences with 750's

Hope this helps

cheers

AshD

[TwoTired]

Last night I ran it and noticed, when I killed the headlight on the highway just to see what happened, that my neutral light and oil light are glowing faintly all the time. The neutral light has always done this when I ride in the rain. Is it an indicator of the possible problem?

First guess is that you probably have a grounding issue.  Likely between engine case and battery NEG connection.  Or, Battery Neg to the wire harness Green buss.

However, the oil switch connects the bulb to Battery NEG when it is supposed to be on.  I can't see how it could glow without current flowing through it, which shouldn't be possible with the oil light switch open.
Maybe you are getting some light "bleed over" from another panel bulb?  Best find out which one is actually on for more precise troubleshooting.

If it gets worse in the rain, maybe the block connectors used throughout the harness are dirty internally and the water helps bridge connectivity between terminals inside those block connectors.  If the "dirt "has high iron, or other other conductive particles in it, that plus water would give an alternate current path.

The neutral bulb can be provided a ground path via the Starter safety unit.  There could possibly be some leakage inside that device from a transistor or diode, incapable of fully turning off.

An electrical technician would need to duplicate the conditions in the shop.  Then identify which circuit is drawing current, and trace that circuit to it's current source, using a voltmeter, ammeter, or ohmmeter (or a combination of those).  A bulb element can only glow when current passes through it.

Cheers,

[B.O.X.N.I.F.E.]

haha tt, like the new avatar.

So the non charging issue... green lead on the field coil had come unplugged. I'm assuming that would explain that. I did test it in case, 4.9 ohms. The stator tested at 1.0 ohms, which didn't match the books .35, but I tested three different stators and they all tested 1.0, so I'm guessing it's a setting on my multimeter not set right? Rectifier passed perfect.

When I disconnected the blocks they were all full of green goo. I had cleaned them all and packed with dielectric grease last year, but I did run balls to the wall on the Bonneville Salt Flats, then rode the bike home through the rain several days and continued to ride it without doing the salt detail I should have. On top of that the connectors were filthy the first time I went through the harness and a second cleaning won't hurt the bike. I'm going to do that while there's snow on the ground.

Last night I ran it and noticed, when I killed the headlight on the highway just to see what happened, that my neutral light and oil light are glowing faintly all the time. The neutral light has always done this when I ride in the rain. Is it an indicator of the possible problem?

First guess is that you probably have a grounding issue.  Likely between engine case and battery NEG connection.  Or, Battery Neg to the wire harness Green buss.

However, the oil switch connects the bulb to Battery NEG when it is supposed to be on.  I can't see how it could glow without current flowing through it, which shouldn't be possible with the oil light switch open.
Maybe you are getting some light "bleed over" from another panel bulb?  Best find out which one is actually on for more precise troubleshooting.

If it gets worse in the rain, maybe the block connectors used throughout the harness are dirty internally and the water helps bridge connectivity between terminals inside those block connectors.  If the "dirt "has high iron, or other other conductive particles in it, that plus water would give an alternate current path.

The neutral bulb can be provided a ground path via the Starter safety unit.  There could possibly be some leakage inside that device from a transistor or diode, incapable of fully turning off.

An electrical technician would need to duplicate the conditions in the shop.  Then identify which circuit is drawing current, and trace that circuit to it's current source, using a voltmeter, ammeter, or ohmmeter (or a combination of those).  A bulb element can only glow when current passes through it.

Cheers,