MOSFET R/R - Kawasaki Vulcan 750 Forum : Kawasaki VN750 Forums
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Where does this wire go?
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post #1 of 9 (permalink) Old 09-30-2019, 06:18 PM Thread Starter
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MOSFET R/R

I'm having yet another stator replacement and am considering a MOSFET r/r soon. My question is how does the charging system fail?

I may be understanding wrong but I believe the stators typically fail after the r/r when it overheats or when the engine itself runs hot for a long time. I have seen people say a failed stator can also destroy a good r/r but am not sure how this happens other than perhaps very high currently from a failed stator.

I will happily spend the extra money for a shindigen if I know it won't fail for a long time. Then again, I'm up I'm the air since I've been considering selling this bike for a great deal on my friend's Triumph Bonneville.
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post #2 of 9 (permalink) Old 09-30-2019, 06:24 PM
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My theory begins with shorts in the junction box.

The shindengen on mine has lasted 5 years, but I did two of the wire mods. I didn't count this year, as I haven't ridden.

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post #3 of 9 (permalink) Old 09-30-2019, 08:30 PM Thread Starter
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So do you think doing the blue wire and two wire mods (if I'm remembering then correctly) with regular r/r would increase my stator life? Are these areas of the junction box causing excessive current to be drawn?
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post #4 of 9 (permalink) Old 09-30-2019, 08:45 PM
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X2 I did away with the junction box.Put in inline fuses, changed a bad ignition switch. An one step at a time I read all the info our great forum has to offer. I can drive Blanch any where now with no problems.These are great bikes once you fix them!

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post #5 of 9 (permalink) Old 09-30-2019, 08:55 PM
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I have no proof of this, but I think the old style R/Rs could be killed pretty quick if the ground wire or monitor wire ever got loose, since that would play havoc on their voltage regulation circuit, and they'd burn themselves up trying to meet a perceived infinite demand. I think the mosfet R/Rs are internally regulated (no monitor wire), so that's not as big an issue.

And heat, of course.

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post #6 of 9 (permalink) Old 09-30-2019, 09:16 PM
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Quote:
Originally Posted by Chris Allunario View Post
So do you think doing the blue wire and two wire mods (if I'm remembering then correctly) with regular r/r would increase my stator life? Are these areas of the junction box causing excessive current to be drawn?
I think it could, possibly.

One thing I like about the Blue Wire mod, it takes 50v ac out of the junction box.

Pretty sure my bike would benefit from a separate fan relay, but I've never gotten to it.

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post #7 of 9 (permalink) Old 10-01-2019, 05:12 AM Thread Starter
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Quote:
Originally Posted by Thorn View Post
I have no proof of this, but I think the old style R/Rs could be killed pretty quick if the ground wire or monitor wire ever got loose, since that would play havoc on their voltage regulation circuit, and they'd burn themselves up trying to meet a perceived infinite demand. I think the mosfet R/Rs are internally regulated (no monitor wire), so that's not as big an issue.

And heat, of course.
You're definitely right about that since they rely on a good ground connection for the excess current that isn't being used. That's the biggest reason I never went to LEDs since my theory is that the r/r is the real failure point which results in the stator overheating from lack of heat dissipation.

Can a bad stator kill the r/r? That's my main concern with the MOSFET one. I don't want to spend the extra money if it's possible for it to fry from the known issues
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post #8 of 9 (permalink) Old 10-01-2019, 05:27 AM Thread Starter
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Quote:
Originally Posted by Spockster View Post
I think it could, possibly.

One thing I like about the Blue Wire mod, it takes 50v ac out of the junction box.

Pretty sure my bike would benefit from a separate fan relay, but I've never gotten to it.
Mine likely could use that too but I went with the tried and true "punch the junction box" method when mine was acting up. After two occasions of it not turning off without it, my fan now cycles properly

Last edited by Chris Allunario; 10-01-2019 at 09:28 AM.
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post #9 of 9 (permalink) Old 10-08-2019, 07:05 PM
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Consider the next step up. A series type regulator. I havena't read about stator failure while using one I've read of at least 3 or 4 stator failures while using a mossfet. Other mc brands with stator problems have been using series regulators for years. I think series type wires up the same but is larger than a mossfet. Brand new they cost $150-200. I bought mine used for $50 a couple of years ago. Beware of fakes. A real one has sh775 stamped on opposite end plug ins. Good luck.
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