Heres some info I found on the subject.
Rect Diodes can only fail one of 2 ways
Open or Closed
Open is a road to nowhere,,,same as if you'd cut the stator wires.
How many "Dirt Bikes" ya think there are in the world,,,Stripped of EVERYTHING possible,,,,,,while the generator whirls away?
Gazillions run like that for Years and Years.
Then somebody Reconnects the Lights,,,and Voila!,,they work fine.
Which proves that a Failed Open Rectifier is harmless to a stator.
A Failed Closed Rectifier Diode,,,it dont care either
It spends half it's life Blocking current,,,and Other half Passing current.
Passing current is a LOT less load than Blocking it.
A failed Rect Diode behaves like merely an extension of the output wire from the Stator.
No Longer a Semi-Conductor,,,it becomes a Full Conductor
Stator dont care if it's wires are 16" long or 16.01".
The trouble is a Closed Diode passes Both sides of the AC wave
Stator OutPut goes Thru Rectifier then Straight to the Battery
If Rectifier is Not Rectifyin' the AC into DC,,,,
WHICH type of Current is the Battery Getting?
Yeah,,,AC.
What does AC do to the battery?
Ever Crosswire Jumper Cables?
Connect Positive directly To Ground?
Grand Mal SHORT.
That's as Short Circuit as ya can get
AC Into a Battery,,,gets Shorted at BOTH Poles on an alternating Basis,,,every cycle swing
Positive Pole gets hit with Negative Polarity
and an instant later
Negative Pole gets hit with Positive Polarity
Does that several dozen times per second.
Like a Tug-o-war of electrons trying to charge the Batt.
It'll eventually Kill any battery.I dont mean Drain it as in "dead Battery"
I mean KILL as in Mortally Wounded.
Obvious question is Why not Immediately?
How can a Batt take that abuse for Days before Dying?
That's complicated.
Simple version includes 2 main principles.
#1 is because a Batt is Constructed to produce a certain polarity and will persist in that function untill it's electrolytic capability is destroyed.
#2 is odd,,,,but even with AC input the Batt is getting SOME small semblance of a charge
At the batts Positive Pole,,it get a Half of the AC wave cycle in proper phase,,,before it Reverses into Negative polarity
So it DOES get a Pulse of Positive Current at the Positive terminal
It Also get a Pulse of Negative Charge at the Negative terminal,,,before IT reverses to Opposite Polarity
And for a very brief instant,,,,On the AC Sine wave,,between the Peak + and Trough -,,,
there exists a Baseline of ZERO Polarity.
And for that brief instant,,,there's No countermanding polarity to oppose what's going into the battery at the moment on a particular terminal.
Gets even more complex with 3phase generator,,,and multi poles.
That's about the point where It's over my head and I quit,,,and leave it to the engineers & take there word for it.
(Meaning Lots of Smile & Nod & pretending I have even a faint Idea what they just said)
Anyway,,,NO a Rectifier cannot really damage a Stator
And Yes,,a Battery can SEEM fine,,,and within a Few days not only be drained but Destroyed.
Simple answer is,,,Replace your Rectifier.
You can test Stator Output according to Repair Manual if you want to.
Battery,,,,,odds are it needs to be replaced also.
You can TRY Charging it--never hurts to Try.
And plenty enough ARE saveable to suggest Charging is worth a try and not totally impossible
Hope any of that gibberish makes any sense
The Theory of everything involved fills entire sections of Libraries.
The Practical application,,,and testing and trouble shooting would fill a small book.
Then when it comes down to What Ya can Do about it,,,you can write it all on a business card.
Test Stator,,,repair or replace if necessary
Test Regulator/rectifier,,,replace if Necessary
Test Battery,,replace if necessary