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Discussion Starter #1
My battery has been giving me signs lately that it's getting ready to let go.
I waited too long. I had a ride for today, and you can guess what happened.
Crank, crank, craaaaaaaaaaank, uhnhghhhhhhhh...... dead. :p

Had to bail on the ride. :(
Bought a new battery, fired right up. :)
So I decided to test my stator and reg/rec.
All tests were done with Highbeam on.
I started with the reg/rec.
First picture is at idle, temp around 190-200F degrees. All warmed up. Second picture is revved to about 4800-5000 rpm.





Every thing seems good to me, Idle voltage is low, but highbeam is on.

So then I test the stator, but before I do, I reference the multimeter into our known electrical sockets of 120VAC.



And then on to testing the 3 legs of the stator. I found no difference between testing the top of the plug vs the bottom (stator side) of the plug.

I was surprised at my readings. I mean, they were consistent among all 3 legs, but i would have expected higher numbers. Like around minimum 45VAC or higher.
1st picture is at idle, and 2nd picture is at 5000rpm.






So should I be ready to replace my stator, or my multimeter?
 

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Looks OK to me?

This year I had my regulator fail on the VFR750 (Common fault, apparently - first time for me) and there - the voltage was constant IIRC. So I fitted a Mosfet reg from a YZFR1 using a connector kit found on Ebay. It's been fine since. If my regulator on the SP were to fail, I'd do this mod again. Can find the items online if you need help with getting these.
 

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From what I see in your pictures, you're taking AC measurements on the Reg/Rec plug side. You should measure the AC voltage on the "male" plug side which is coming from the harness. All 3 yellow wire pairs should read as you can see in my video.
 

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In addition, take resistance measurements on the three yellow wire pairs as well as each yellow against the engine's ground (any crankcase cover's bolt will do).
Yellow to yellow should read 0.2-0.5Ω (20 deg.C- 68 deg.F) and NO continuity between each yellow terminal and the engine's ground

Service Manual's page 350
 

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Discussion Starter #8
Ok Makis, guess I'm taking the tailsection back off!
I tried to test the stator wires exactly as you pictured - by disconnecting the plug and probing the stator side. (I hadn't seen this video yet-wasn't sure if this was the right way) So I hooked it up, hit the starter button and nothing. Wouldn't start. So I plugged it back together and resumed testing the way you see the pictures.
I don't know why it didn't start - seems like yours did?? I'll go try again.
And I'll do the Ohm testing too.

To be continued...
 

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Make sure, before start testing, that you have a fully charged battery cause when you disconnect the Reg/Rec the battery will be working at 100% of it's capabilities.
So, no lights (remove the headlamp's connector) or anything else unnecessary should be powered while taking AC measurements.
And never ever plug or unplug the Reg/Rec's connector while the engine's running.
 

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Discussion Starter #10
Ok, I tested again today. I forgot about having the lights on. So they were on.
Thinking it through, I guess it wouldn't affect the test of the stator at all. right? It just would deplete your battery kinda fast.
I did the test quickly, only needed about 2 minutes to test all three pairs. And my battery was a fully charged brand new Yuasa.

Here's my numbers today testing at the stator side of the plug after disconnecting it.

First picture is at idle, all warmed up.



.
.

This picture is at roughly 4000 rpm.



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.

And this last picture is testing the Ohm resistance of all three pairs. They all danced back and forth from 0.5 to 0.6



And my last test was to check ohms from each leg to ground. All three were infinity.
Looks like my stator and reg/rec are doing ok.

Thanks for the help guys.
 
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