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Discussion Starter #1
Anyone ever experience this? I have a Heads-Up voltage monitor on my Vulcan which indicates the voltage level of the charging system by changing the color of a single LED. It has recently indicated that the voltage actually drops as RPMs increase! What the.... So, this morning I put a meter on the battery and here's what I got:

1500 RPM ~ 13.2 VDC
2000 RPM ~ 13.4 VDC
2500 RPM ~ 13.5 VDC
3000 RPM ~ 13.7 VDC
3500 RPM ~ 13.5 VDC
4000 RPM ~ 13.2 VDC
4500 RPM ~ 13.0 VDC

This behavior started with a questionable R/R which I installed after mine failed. Stator output leads are fused and the old R/R didn't affect the stator at all. I plan to install a new R/R and I hope that will solve this, but how the heck can this behavior happen? I guess I need to test the output voltage of the stator at the same RPMs, which I have not done. The only other symptom is that this goes away when the engine becomes fully heated up.
 

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Personnaly, I'd remove the fuses from the stator leads. It's been the experience here that if one leg blows, the other 2 take up the slack and it ends up damaging the stator and the R/R anyway.
You may want to see if one leg's fuse is blown and then proceed with trouble shooting from there.
 

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Discussion Starter #3
Yes, but...

The usual failure mode of the two remaining stator legs is overheating from the additional current draw. I installed an oil injector which floods the stator with engine oil to constantly cool it so extra current, up to the 15 A fuse limit, won't overhead my stator. Between the fuses and the oil cooling, I don't expect to ever lose my stator again. After the second stator change, I got smart.
 

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If your engine oil overheats, you will still get stator overheating unless you also installed a separate oil cooler.
Be that as it may, you may still have blown one leg on the stator or your R/R is out of spec or both. The only way to know will be to test them/examine the fuses. The voltage test only tells you something is wrong, not what. Is your R/R in spec for resistance? Is the stator putting out the correct level of AC for the RPM? Is the stator in resistance spec between legs and each leg and ground? Without the answers to these questions, any other guess is a shot in the dark.
 

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But why do we have so many problems with our stators and R/R's?
 

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But why do we have so many problems with our stators and R/R's?
Planned obsolescence... if the bike worked as well as it could, Kaw service people would be out of business.

That's the economic explanation. The technical explanation has to do with the location of the r/r and a system that is running at pretty close to max capacity, just on a normal day.
 

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In short (no pun intended..) ALL stators go out. It's one of the reasons they only have a one year warranty. Usual mileage is probably 20,000 or so or two to three years.
However, most other stators are easier to swap out. That is the one thing that makes our stators a PITA.
There arer exceptions. Reports of bikes with 80,000 or more miles on the original stator. Most of these get regular maintenance, don't overheat and do not tax the electrical system. Even with that, there is no gaurantee a stsor will last forever. They are made by humans after all.

BTW, I also wanted to mention that if the voltage straightens out once the bike warms up, chances are it's NOT a stator problem. One of the problems is a short to ground AFTER the bike warms up and you would see the voltage drop to 12.5 or there abouts.
 

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Discussion Starter #9
Well, I tested the stator output this morning with a DVM and the stator is working normally unloaded, without the R/R connected. However, when I connect the R/R, the output is being dragged down as the RPMs increase. So, the full symptoms are:

  • Stator output normal when not connected to R/R: ~50-70 VAC
  • R/R output (battery voltage) rises with RPMs to ~3000 RPM, then decreases with higher RPMs
  • Stator output follows same levels when connected to R/R (that makes sense as the output leads are only isolated from the battery by ~0.7 V drop through rectifier diodes)
  • Stator leads are all ~20 MOhms from ground
I have never gotten the correct R/R resistance readings, even on a new unit that functioned correctly, so I'm not sure what to make of that.

So, I just ordered a new R/R from RM Stator in Canada. I talked to a guy (Eric) about the current capacity of the RMR260, standard application for the VN750, and he said they are contract manufactured by a company and he's not sure of the actual specs. He pointed out that their 'Universal 500W Rectifier' is a lot heavier duty. That's what I ordered and I will adapt its connections to my wiring harness. 500 watts is 66% more power handling capacity than our 300 watt system! Waahoo!

See: www.rmstator.com

As a side note, he is going to investigate whether they have the mating connector to our stock R/R. If so, they will sell them so Vulcan owners can repair melted R/R connectors. He thinks they have the connector housing and female stake-on connector inserts, but I'm going to confirm that with him when I get my universal R/R.
 

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Discussion Starter #11
Hi All, I want to follow up on this problem with the solution. I have been on business travel and the sick and then ordered a replacement OEM R/R trying to solve this problem, so it has taken a while to resolve, but it turns out that the negative battery cable was loose.

Last Friday I started troubleshooting the problem after I replaced the R/R and still had the same symptoms detailed above. I thoroughly tested the stator, fuses, R/R, and wiring and everything checked out fine. I surmised that it must be the battery going south and started to remove it and found the negative battery terminal bolt had come loose. Tightened it and, Viola! the charging system works normally again. Not too surprising, but good to share here. Reminds me of the first principle of troubleshooting: "Start with the simple stuff first."
 

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I think I speak for everyone else here when I say, "Thank you" for this final feedback to the story--glad to know it had a happy ending!!!...:D

I guess one (other?) moral of this story to the rest of us would be the importance of maintaining clean, tight electrical connections. Also--can anyone say, "dielectric grease"?
 
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