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Charging issue

2K views 27 replies 5 participants last post by  Odin'sRavens 
#1 ·
Hello, working on a friends bike. His bike kept dying with a dead battery on side of road going to work. It is a 1993 Vulcan 750.
Him and his friend diagnosed it without me as the regulator and replaced that to no success. They than diagnosed it as a stator there enters my issue.
The bike gets dropped off to me and after three times of pulling the motor (I’m a pro now it’s out in 1.5 hours) it’s back together and running (different leaks that appeared were reason for pulling repeatedly).
So I do the stator rewire the burned harness bullet connectors and start it up. The battery is new and fully charged. I got 12.4 volts at idle and 12.9 at ~3100. Not good enough to my understanding.
I read the forum and pulled the headlight fuse. I now at 13.2 at 1500 rpm (yay) but when I rev it to 3000 it drops to 13 volts. Is there any thing else to do or check? I can’t figure out why it is behaving like this. Wire connections appear to be clean.
I haven’t tested the stator or the regulator as they were new and do appear to be working to some capacity.
Thank you
 
#2 ·
Have to start with stator testing, ... What are the AC volts?

If that checks ok, test the R/R, next I suppose I would think about the Blue Wire and Two-Wire mods to take 2/3 of the JB out of the question.

Any extra lights added to the headlight circuit?
 
#3 ·
I will have to check the stator tomorrow. I know it’s not the best to skip but didn’t do it (the wires are impossible to get to with my hand size so need help). There are no accessories on the bike other than a hook up for tender (not currently on the bike anyways).
 
#4 ·
I checked the stator everything is right on spec. The regulator I believe is good (I’m not getting infinity but getting even numbers across terminals (6.5 m ohms). Would this be sufficient? I would think if it was a bad regulator all the leads would not be the same number.
So I cleaned the connections I had to deal with all are clean good and tight. The bike goes up right to about 13 volts at 1500 rpm than flat lines to even slightly drops when revved to 3000.
 
#6 ·
That is not high enough to charge the battery, you still have a problem.

When you checked the stator and R/R what checks did you do?

Stator should look like three wires joined together at the far end with no connection to ground using an ohmmeter. There should be AC voltage of at least 40 and maybe as high as 70 v between each pair of the three wires when running and the R/R is disconnected.

R/R is harder to check , simply measuring ohms across terminals is not really adequate, if you get the AC volts in from the stator above and don't get ~14.5 volts out it is the R/R thats dodgy.

Make sure the R/R sense terminal is connected directly to the battery and not through the JB or any other place. Make sure the R/R is grounded properly and remake all the two part connectors jst make sure they are getting good contact
 
#10 ·
The R/R should have 6 connections, three go to the yellow stator wires in any order, thats the power input.
There will be a 12v (nominal) out and a ground. Get these connected as close as you can to the battery with as few joints in the way as possible.
Then there is a "sense" connection, this provides the feedback on the actual voltage in the system. On a stock bike this takes a long journey that can have voltage drops due to poor connections. Make this connection as close as you can to the battery + terminal if not actually on it.

For a lead acid battery "The actual resting voltage, or the voltage a battery will settle at 12-24 hours after being removed from the charger, is closer to 2.1 volts per cell, or about 6.4 volts for a 6v battery, and 12.7 volts for a 12v battery. These numbers assume 100% healthy cells, and may vary a bit lower for older batteries."

So your 13v is not enough to charge the battery, you need to see 14.5v or better.
 
#11 · (Edited)
#13 ·
The replacement was a ricks electric. I spoke with a friend who says if it’s supposed to be infitinity resistance and I’m getting 6.5 m ohms that is too low a number compared to infinity. Conveniently I looked up the part and I have a zn700ltd from 85 and it’s the same regulator. Going to try that all the grounds and plugs are good and clean. I can’t say the wires are not corroded inside but nothing is getting warm or hot as I’d expect if it was shorting to ground.
 
#16 ·
So I tested the regulator with it out of the bike and did not get the tests to come up as the chart indicated. Said yay new regulator. Tried the resistance chart with new one got extremely similar numbers to the replacement. Plugged in new regulator exact same conditions 13.1-2 volts at 1500 rpm. It drops to 12.95 at 3000.
What are the chances of two new replacement regulators being bad? Or am I right to assume this is elsewhere in the wiring. As stated earlier the resistance test and voltage test of the stator were in spec.
 
#17 ·
Just tested a new idea. Rechecked the stator it’s still infinity to ground at the plugs on stator end. I checked the resistance of the wires from the harness. I have infinity on 2 of three and 12m ohms on the a3 wire at both ends when I just do continuity between both ends I have .1 ohms the other 2 just read zero. Is there any reason a single wire would be different other than a short in harness?
 
#18 · (Edited)
The two wires with infinity are broken?

edit: >>> Somebody check me on this. Thorn, Tony, MTB .. anyone. I've struggled with the definition of 'infinity' in this sense lately.

Experts say infinity to ground on a stator test is good. Meaning no connection to ground.

So infinity on the wire test means no connection?

My Meter only shows OL, Open Loop, have not seen ∞ , the infinity symbol.
 
#19 ·
Ok last thing. I cut the battery wire and negative and wired with a same piece of wire directly to the battery. Perfect 12.5 volts at 1000 13 volts at 1500, and 14.2 at 2500 and up. Can I just wire this like this with a more permanent situation (thicker wires with round hooks currently I just have a wire spliced on with it wrapped around the battery to test it)
 
#21 ·
12.5v at idle isn't enough, but might be ok if you don't sit around idling. The problem will be in stop/go traffic when the fan is running. Everything at that point will be running off the battery. ... ignition, headlight, fan, brake, tail, running lights, etc.

14.2v @ 2500+ will work.
 
#24 · (Edited)
Last question after a bunch of testing it appears about 13 at idle and 14.2 at 3000. When the fan is on at idle is drops to 12.5 when brought to 3000 it is 13 to 13.2.
Just checking that this is an acceptable range I know the fan is a large electrical load.
Bike runs good now onto the next issue (seperate post) of why I am getting a burning smoke by the rear exhaust (nothing touching that could make smoke other than the rubber motor mount spacers.)
 
#27 ·
The bike rarely sits and idles it’s basically a work commuter for the guy who owns it. Also that is at 900-1000 rpm where I set it. I see now that idle should be 1100-1200. I’ll bump it up and see what I get. At least it’s at 14 over any rpm where the clutch is out
 
#28 ·
Hi all,
I got my vulcan about 2 years ago w/ 6500 miles on it and have been doing basic maintenance and cosmetics.

Found my battery dead last week and started poking around for what to check.

I hadn't been watching the volt meter and it turns out I was getting nothing to the battery while running.

I pulled the r/r and checked the continuity/ohms on the pins and it's not reading anything.

I checked the continuity between the yellow stator inputs and they seemed ok but they also had a reading to the chassis. Two of the pairs seem to put out decent AC voltage and the other was lower.

At this point, I'm working on the assumption that the r/r is dead and the stator is shorting.

Based on the info I found here, I'm looking at getting a super mosfet kit from roadstercycle. But I'm not sure of the current "best practices" when it comes to the stator.

I saw the $400+ kit from TOC but it doesn't include the stator.

I might have the resources to do the machining on the cover and get one of the plate kits from gcextreme or similar.

If I get into the motor far enough to get the cover off, what else should I be doing?

Thanks in advance for the support and for keeping this great source of information alive!
 
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