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fubar
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12 Posts
Discussion Starter #1
I just bought a 1986 VN750 two weeks ago. I'm still learning to ride, so I stalled out a few times Thursday. This may have something to do with the following problem:

Symptoms:
Stalled out, couldn't start engine again
Battery was dead

What I've done:
Recharged the battery to full
Tested it on a battery tester. Checked out fine.
Took her out for a ride, seemed OK. The previous owner installed a voltmeter and relocated the regulator/rectifier as detailed in other posts on this forum. The voltmeter is connected at the battery.

Voltmeter readings:
12.8-12.9 VDC bike & ignition off
~12.3 VDC ignition on, engine off
About the same when the engine is on, and idling

Revving the engine doesn't change the voltage reading. The only thing I found that changed the voltage measured was actually getting the bike going in a higher gear (>=3) and at an engine speed of about 3k RPM.

This is from memory, but I'll try to borrow a decent voltmeter and measure voltages directly.

Has anybody experienced anything similar, or have any suggestions on what I can do to troubleshoot further?
 

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fubar
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12 Posts
Discussion Starter #2
Forgot to mention: Removing the positive lead from the battery when the engine's warmed up and running will cause it to sputter and die.
 

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Premium Member
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3,505 Posts
Forgot to mention: Removing the positive lead from the battery when the engine's warmed up and running will cause it to sputter and die.
I learned from these folks last year (after my regulator went in Gettysburg and some helpful soul was trying to diagnose the problem) that removing the pos lead isn't a diagnostic tool on these bikes. Didn't cause any additional problems with mine, but just a caution.

At idle (around 1100 rpm), your battery will not be getting recharged - the charging system doesn't kick in until around 2500+ rpm. So you can idle for a long period of time, and just watch the voltage slip away. If you can twist the throttle and gets the revs up to 4-5K, your voltmeter should show an increase to about 13.5 or thereabouts. If it's not, first check your regulator (especially since it's been relocated) - I have a heckuva time getting the measures that the Clymer's calls for, but if the battery's not recharging properly, that's your first (and most likely) culprit. Also, and maybe you posted this and I missed it, how old is the battery?
 

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fubar
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12 Posts
Discussion Starter #4
At idle (around 1100 rpm), your battery will not be getting recharged - the charging system doesn't kick in until around 2500+ rpm. So you can idle for a long period of time, and just watch the voltage slip away. If you can twist the throttle and gets the revs up to 4-5K, your voltmeter should show an increase to about 13.5 or thereabouts. If it's not, first check your regulator (especially since it's been relocated) - I have a heckuva time getting the measures that the Clymer's calls for, but if the battery's not recharging properly, that's your first (and most likely) culprit.
OK, I'll try that tomorrow.

Also, and maybe you posted this and I missed it, how old is the battery?
1 yr old, maintenance-free Yuasa
 

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Now what
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400 Posts
For one reason or another your bike isn't generating any electricity. It's running off the battery. Probably runs for about 20 minutes on a full charge. Go here, http://tinyurl.com/dq2h7 ,scroll down and download the fault finding chart. It'll pinpoint the problem. Hopefully it's just a bad connection somewhere. Could be the stator. You'll need that new voltmeter to run the tests.
 

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Registered
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236 Posts
I had issued with mine shortly after I bought it too. Hopefully it's just a loose connection or the r/r. Look here for some help that I got from the folks here in diagnosing my problem. Mine turned out to be the r/r which I got from bikebandit.com for ~$90.

Good luck.

Tony
 

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Premium Member
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382 Posts
The VN750 needs the battery to complete a circuit - you pull off either main cable off of the battery (or if just happens to loosen up), the bike will die.
 

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fubar
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12 Posts
Discussion Starter #8
Actually, removing the battery, charging it, re-tightening the leads and using some dielectric grease seems to have done the trick. I'd still like to check the stator yet. Haven't had a chance to tear into the bike yet. Thanks for your suggestions!
 

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Growling at the World...
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564 Posts
Actually, removing the battery, charging it, re-tightening the leads and using some dielectric grease seems to have done the trick. I'd still like to check the stator yet. Haven't had a chance to tear into the bike yet. Thanks for your suggestions!
That is why we always sugest the simple things first. That 1986 probably has a bunch of corrosion that needs to be cleaned up. Check all your grounds, run the harness and look for frayed wires, bad connections and funk or rust. By cleaning up your battery connection you have given the DC current a clean path to the battery. Great job...
 
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