introduction and diagnosing the charging system - Kawasaki Vulcan 750 Forum : Kawasaki VN750 Forums
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post #1 of 9 (permalink) Old 07-14-2006, 06:43 PM Thread Starter
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introduction and diagnosing the charging system

hello everyone.

quick introduction and then a few questions. in april i purchased a 91 vulcan 750 in san francisco and rode it cross country to my home in boston. the trip was amazing and the bike performed beautifully until i hit pennsylvania where the charging system started going. one tow and a few battery charges later, i made it back to boston at the end of may. since then the bike has been in the shop once; the mechanic said he couldn't verify the charging system problem. by the time i got home from the shop, the battery was dead again.

rather than take the bike back into the shop (and waste another few hundred dollars), i've decided to tackle the problem myself. i've researched the problem online and joined vroc, the yahoo groups 750 group, and this forum.

the bike has 23k miles on it and i just installed a yuasa mf battery that i charged with a battery tender. at idle (1000rpm), the voltage across the battery terminals is 12.4v. when i rev the engine up to 4000rpm, the voltage increases to 12.7v.

i tried diagnosing the problem at the R/R. after unplugging the 6-pin connector, i took resistance readings as outlined on page 15-18 in the service manual. several of these readings are way out of whack and so i need to replace the R/R.

i also disconnected the three alternator leads and took resistance readings. unlike the readings i took at the R/R, the meter jumped all around. the most stable readings i got between the contacts were around .5 ohms (within the spec). still, at points the ohmmeter read .7 and .8. i'm planning to replace the R/R and hope the stator is all right.

questions:

1. is there a better way to get stable resistance readings on the alternator leads? i cleaned the wires well but still the meter jumps all around.

2. i took all these readings with the engine off. is this correct?

3. if i replace the R/R and the stator IS in fact bad, could the new R/R be damaged by the bad stator?

thanks much. really appreciate the help.
paul
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post #2 of 9 (permalink) Old 07-14-2006, 07:10 PM
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The answer to number 3 is no. I bad stator won't hurt a regulator. Check the voltage outputs from the stator at 4000rpm. They should be 40-70 volts AC. If not, then it's the stator. Actually, here's a better deal. Go to:
http://www.electrosport.com/Images/fault_finding.pdf

I've tried resistance readings on a new known good r/r, and I can't always get the right stuff.

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relocated R/R
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post #3 of 9 (permalink) Old 07-14-2006, 08:03 PM Thread Starter
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question regarding fault_finding.pdf

thanks cegodsey.

with regards to the electrosport fault_finding.pdf document, i'm down to the step that reads:

"You've got a permanent magnet alternator system. Let the engine idle, and connect the black multimeter-lead up to the battery(+). Connect the RED multimeter lead up to the RED (or WHITE/RED = Kawasaki) output wire of the RR. Leave the RR connected up to the bike. Check the reading on the meter. Leave the engine idling!"

how do i logistically do this? i can connect the black multimeter-lead to the positive battery terminal... no problem. i don't have a white/red wire which connects to the R/R... i have a white wire which connects to the lower righthand pin of the R/R. the instructions tell me to leave the R/R connected to the bike... do i just shove the multimeter probe into the back of the 6-pin connector alongside the white wire? or do i need to remove the white wire from the 6-pin connector?

thanks. sorry for the newb questions... this is the first time i've stepped into the mechanics' shoes.

paul
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post #4 of 9 (permalink) Old 07-15-2006, 12:32 AM
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Quote:
Originally Posted by global_recon
the instructions tell me to leave the R/R connected to the bike... do i just shove the multimeter probe into the back of the 6-pin connector alongside the white wire? or do i need to remove the white wire from the 6-pin connector?
Just jam it in there. At times I've taken i piece of uninsulated wire, wrapped most of it around the probe, and left enough of an end to stick into those tight spots between the wire to be tested and the connector. They make probes like this, and some with alligator clips. I usually just make do.

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Kuryaken grips
relocated R/R
de-badged
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post #5 of 9 (permalink) Old 07-15-2006, 06:56 PM
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Same problems getting ohmmeter reading

I'm having similar problems getting a steady ohmmeter reading from my stator wires. I did the "jam it in there" thing, but the meter jumps around and ultimately returns to "0." Am I doing something wrong, or is the stator just shot? THe R/R is definitely shot (I already did those tests), so I wanted to see if I also need to test.replace the stator.

For the ohmmeter - I have a digital one that allows me to set the decimal point pretty much where I want to. I know for the r/r I needed to set the meter at R x 100 (00.?) and the ohmmeter at Rx1 for the stator (0L.?). Am I doing something wrong?

Thanks for any help you can offer (if I can avoid having the pull the stator, i will be very, very happy...).

Cindy Robins
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post #6 of 9 (permalink) Old 07-15-2006, 08:05 PM
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Cindy, are you going by the fault finding PDF? It says what to do if you get 0L

http://www.electrosport.com/Images/fault_finding.pdf.

2000 A16
Drilled baffles
$65 leather saddle bags
Kuryaken grips
relocated R/R
de-badged
25,000+ original owner miles
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post #7 of 9 (permalink) Old 07-16-2006, 10:25 AM
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Thanks, I did look at that pdf briefly yesterday, but never made it all the way to the bottom. I also got myself confused about k ohms and m ohms, but this makes it pretty clear. I'll give it another shot and see what comes up on the meter - I go between feeling like, "Ah, I can do this; just need to take my time," to being completely overwhelmed at what lies ahead. Can't even fix my lawnmower at the moment...

I'll give it another shot and post back my readings.
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post #8 of 9 (permalink) Old 07-16-2006, 02:37 PM
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Readings from my multimeter - perhaps...?!?

Ok, I set the multimeter for ohms, but put it on "auto" so that the meter could decide the appropriate way to measure the resistance. I just measured across the three yellow wires (crossing around positive and negative, so I've got six total readings), and although there was some initial jumping around, my measures run from a low of .4 to a high of .7. Ohms, not k ohms or m ohms. For the r/r measures, I was getting in the hundreds of k ohms (I guess that counts as "infinity"?); and from an earlier diagnostic run oin the bike - when it was all in one piece - the battery went from 12.79v cold to 12.0v idling after I'd ridden it a couple of miles. Then it wouldn't re-start (clearly not charging), so I started pulling pieces.

Sooooo, I know the readings I'm getting on the stator are "close" to the recommended measures, and if I went out and measured again, could be a little different. But let's say I replace the r/r and put in a new MF battery. If I am wrong, and the stator is blown but I've not replaced it, how would I know? More to the point: If I think the stator is ok and I replace only the other parts(r/r and battery), but the stator is really not okay, what additional damage will I do to my bike?

Hot day here, but beautiful - too bad I'm sitting in the garage...

C
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post #9 of 9 (permalink) Old 07-16-2006, 03:34 PM
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A bad stator won't hurt anything. So replacing the other parts is OK.

With the bike running, check the voltage coming from the yellow wires - yellow wire to yellow wire (and maybe even each yellow wire to ground). If the stator is working, then you should be getting greater than 14 volts AC, up to around 70 volts or so. I think checking the voltage output has gotta be better than checking the resistance of the stator.

2000 A16
Drilled baffles
$65 leather saddle bags
Kuryaken grips
relocated R/R
de-badged
25,000+ original owner miles
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