Possible cause of stator failiure - Kawasaki Vulcan 750 Forum : Kawasaki VN750 Forums
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post #1 of 5 (permalink) Old 05-25-2014, 11:13 AM Thread Starter
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Question Possible cause of stator failiure

Question: How many people shut off the engine using the engine stop switch, and how many just use the key switch?
I may be way off track with this, but what I know is that if you shut down a marine diesel engine by turning the key, you risk damaging the alternator (stator). You must use the engine stop switch. The problem has something to do with driving current back through the alternator after the ignition cct has been switched off. I'm told that this has the effect of turning the alternator into a motor, causing irreparable damage. This would be more likely to occur if you give the engine a good old revving just as you shut off the key, which I know some people have a habit of doing.
As I say, I may be well off the track with this, but it's worth thinking about.

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post #2 of 5 (permalink) Old 05-25-2014, 11:17 AM
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It would have nothing to do with that, since the stator is not an alternator. Current from the stator is a 1 way street to the R/R.

The biggest issue is it is not bathed in oil enough, coupled with a bad stock regulator location, and a old style regulator (shunt style). Another issue is the connectors from the stator to the R/R. Since they're not soldered, it eventually causes a point of resistance over time. Cutting them out and soldering helps.

Edit: For clarity

1986 Kawasaki Vulcan 750
NGK Iridium Plugs #7803/DPR7EIX-9
Duralast Gold ETX15 AGM Battery
Coastered & Shaved
Metzeler ME880 [110/90-19, 170/80-15]
Balance Dampers Replaced
Tuxedo Mod
Rebuilt Forks w/ Progressive Springs
V&H Cruzers
VN750.com Grill Cover
Meanstreak Seat
Emgo 23-92411 Handlebars

1990 Kawasaki Vulcan 750

1998 Honda VFR800 FI

2014 Honda VFR800F

1989 Pontiac Firebird Formula 350

Last edited by thtanner; 05-25-2014 at 10:08 PM.
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post #3 of 5 (permalink) Old 05-25-2014, 12:01 PM
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I'm interested to see what electrical gurus have to say
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post #4 of 5 (permalink) Old 05-25-2014, 12:21 PM
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This is what I was told...

Stators fail because the insulation on the wires breaks off and effectively "shorts" them out. Why this happens can be due to age, a poor choice of insulating material to start with, overheating or possible oil contamination.

It has always been believed here that maintaining proper oil level helps reduce stator failures...but even motors with high oil levels can fail.

It also should be noted that many other bikes have stator failures, but no one makes a big deal about it because their stators can be replaced real easily and quickly.

I don't think marine diesel alternators have anything to do with Vulcan stators.
All autos I've driven with alternators turn off at the ignition key.....

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Last edited by Knifemaker; 05-25-2014 at 12:25 PM.
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post #5 of 5 (permalink) Old 05-25-2014, 09:45 PM
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Got to agree with thtanner and KN on this. The diodes in the rectifier inside the R/R will stop 95% of any back current from the battery and converting the alternator into a motor. I've played around and have turned PM and induction motors into alternators using diodes and capacitors in a effort to make small low cost alternators.

As KN said most alternators fail from damage to the insulation.

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