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Discussion Starter #1
So, I'm cruising at 60MPH on a cool spring evening in Colorado (Denver altitude, not in the mountains) on my 1990 stock 750 (with about 23,000mi.), and the engine starts to momentarily and intermittently cut out in a manner very similar to the POOGS problem. However, the engine did not die, and out of the corner of my eye I notice that the tach was momentarily spiking UP in RPMs as the engine seemed to hesitate (as much as 1000-1500 on the dial). The problem has persisted now into a second day, and it seems to happen at all speeds and in all gears. I cannot determine yet if it happens with the bike just at idle.

A forum search led to one thread (#19054) which suggested a faulty/loose battery ground connection. I immediately checked that, but it does not "seem" to be the issue. The very last thing I did as far as work on the bike was to synchronize the carbs, but I cannot imagine this would be the cause of the problem.

I realize the tach is electrically (not mechanically) driven so I am posting this in the Electrical Section, but since I am at best just an amateur mechanic, I seems it could be any number of things. Does anyone have other suggestions for a strategy to find out what the likely source problem is?

Thanks for any help you can offer.
 

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1986 VN750
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I still think it's a ground. Every time mine did that, it was one of the ground wires. (and it did it 3-4 times after I first got it.. had to keep tracking down the various ground cables, and using some loctite.)
 

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..have a vulcan good day!
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I still think it's a ground. Every time mine did that, it was one of the ground wires. (and it did it 3-4 times after I first got it.. had to keep tracking down the various ground cables, and using some loctite.)
the tach operates off the Front (#1) Cylinder.....

so yes, absolutely x2 on thTanners remedy. :smiley_th

...check/clean ALL connectors...
 

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This sounds an awful lot like what happened to me right before my bike went out the other day. Mine turned out to be a couple of loose connections and a loose ground.

It's a bit of a pain but the best thing to do would be to carefully check over all of your electrical connections to make sure that nothing came loose.

If they aren't soldered on I would check the ring terminals to the battery to make sure that they are still tight as well.
 

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Crowley
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Make sure also your key is not in the "wiggled a bit to the left of 'on'" position.

I had an issue starting my bike - it wouldn't start with the key in the on position. I had to turn it slightly counterclockwise to get it to work. This slight counterclockwise position was giving me the same issue you seem to have.
 

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Make sure also your key is not in the "wiggled a bit to the left of 'on'" position.

I had an issue starting my bike - it wouldn't start with the key in the on position. I had to turn it slightly counterclockwise to get it to work. This slight counterclockwise position was giving me the same issue you seem to have.
I was just about to suggest removing the puck under the key tumbler and cleaning the contacts in it.
It sometimes cuts out completely, but has been known to also give intermittent issues and symptoms like a loose connections.
 

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clean all connections while doing this you may find the issue. there is a ground that goes to the engine. its on the back of it on the right side. use contact cleaner and 1000 grit sandpaper for connections held by a bolt. a nail file works good too. i used a welding tip cleaner set pretty much the same as a carb cleaning set on the harness connections. get some electrical grease to prevent more corrosion once cleaned.
good luck hope its something simple.

Sent from Motorcycle.com App
 

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Try jumper cables to the battery from the car. If it runs like new, the battery is taking a dump. Had similar problem a week ago, ran great on the cables from the car, died when they were off. Replaced the battery and runs like new.
It may be the battery is shorting internally.
Bronson.
 

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Discussion Starter #9
Thanks to everyone for the, as usual, excellent advice and willingness to help out a fellow rider.

I have not yet put on enough miles to say with certainty that the issue has been resolved, but I think it has. I did not see any faulty connection/ground issues, but I did clean and re-seat the major ground points at the battery, frame and engine block. Also cleaned up the left side ignition coil wire connector tab for the black wire.

If all goes well in the next day or so, I will post a message to share my final conclusions. Suffice it to say this for now: if you don't usually get your bike wet while riding, you just might be surprised by what happens when you do!

Thanks again.
 

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hope you got it fixed. let us know the anticipation is killer lol

Sent from Motorcycle.com App
 

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Try jumper cables to the battery from the car. If it runs like new, the battery is taking a dump. Had similar problem a week ago, ran great on the cables from the car, died when they were off. Replaced the battery and runs like new.
It may be the battery is shorting internally.
Bronson.
good point!

And...where the hell have you been bro?
Glad you are still around...hope all is well!
 

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Discussion Starter #12
For those of you interested in this thread, here is the rest of the story. It consists mostly of my observations, and I encourage those with more knowledge and experience in these matters to offer their analysis and conclusions.

There are two sets of wires exiting the stator housing, each in its separate sheath. One set of three wires connects to the voltage regulator to power the charging system. The other set of four wires transmits the signals from the pickup coils into a four pin connector in the harness near the interior mid-line of the bike beneath the fuel tank. In the course of checking my grounds and the tachometer wiring circuit, I disconnected this set and pulled the sheathed bunch out from its normal position. In doing so, the normally elevated connector end of the set dropped below the stator exit end. Water poured out of the sheath!

On my bike, these wires exit the stator with about an inch of a rubber cover or extended grommet, then the actual wire sheathing run starts all the way up to the connector. But there was a space between the two coverings, and the start of the sheathing run was not tightly sealed. Upon watching the water drip out, I began to think about the last bit of riding I had done.

It’s pretty dry here in Colorado and I avoid riding in the infrequent rain. However, I was caught in a shower on the ride immediately prior to the appearance of my problem. It was not a huge amount of rain, but it was more than I had ever ridden this bike in previously and it was at highway speeds.

So I then removed the sheathing completely and carefully inspected each of the four wires from the pickup coils. I could not detect any obvious defects in them or in the ends of the top end connector, but there was plenty of moisture (though none in the connector). I dried things out and continued to inspect/clean grounds and the electrical connectors on the left-side ignition coil. Again I found no obvious signs of trouble.

I temporarily reconnected the pickup coil wires, and fired up the bike. It ran fine at idle and at higher RPMs while sitting on the center-stand, so I re-sheathed the bunch and put everything back in place and took her for a ride. No symptoms. I have since put over 100 miles on the clock, and she has run just fine.

I cannot say it was absolutely not a faulty ground, but I am inclined to believe the water had something to do with it—either in the pickup coil wires or somewhere else on the bike (wouldn’t that be a “short”). In any event, I look forward to hearing what others may have to say. I know a lot has been written on this forum about the other wire bunch coming out of the stator! Consider this a contribution for the other set.

Thanks to all for your help.
 

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Glad you got it running again....and thank you for following up and telling us what you found.

Since the signal coming from the the pickups are pulsed, and is carried by paired wires that are not exactly of high quality, I can see how moisture would effect the signal.
I have seen the same thing with coaxial leads and paired wires which have had water seep into the sheathing and fill the air gap.

I think you found your problem!!
 

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Discussion Starter #14
Update from OP

As you can see from an earlier post, I thought I had fixed the problem. However, the symptoms returned after about 150 miles so the investigation continued. I still thought the issue might be water-related, so I decided to look at possible problem areas one at a time. I chose the Kill switch and Start button on the right-hand controls as a starting point.

I opened the switch housing and took apart the mechanism for inspection. Nothing seemed obviously wrong. There is not much you can do with the red Kill switch, so I bathed it down with electronic contact cleaner from every angle possible and then blew it dry with compressed air. I also cleaned up the Start button contacts since they were right in front of me. After I put it all back together, I rode for about 20 miles with a full shut down at mid-point in the ride. No symptoms! Did I get lucky or is it just coincidence?

That was almost a week ago, and I have put on at least another 100 miles without a problem. None of that riding, however, has been in water of any kind. Since it is a Kill switch, I can easily understand how dirt/water might have caused the engine to momentarily cut out. However, since I never will understand how electrical signals work anyway, I have a hard time seeing why that switch would also cause the tach to spike.

If the symptoms return, my next step will be to pull the Key switch for a good inspection and cleaning.
 

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Discussion Starter #15
OP Update

I think this is my final post in this thread, but I wanted to add this information.

My original theory about the problem I had focused on water causing a short somewhere in the tachometer/timing wiring. I now believe this theory was incorrect. The problem, while seeming to be solved, continued to reappear--usually after riding for 50, 60 or more miles. I was stumped.

In further exploration of the Verses, I came across a post which referred to the possibility of a short in the tach wiring in the area of the gauge cluster, so I pulled mine apart and took a look. I soon realized that the several wire bundles had been routed in a completely inappropriate fashion. So much so that a pinch, crimp or other fault was possible. I first examined the wiring as carefully as possible, but again I could not see an obvious defect. I then figured out the proper layout of the wire bundles and their routing and re-assembled the gauge housing. All possibility of pinching and crimping seemed to be eliminated.

That was several hundred miles ago, and the symptoms have not returned once. If you do suspect a tachometer wiring-related problem, you may want to take a look at this location. I wish I had taken some photos to share, and perhaps the next time I open up the housing, I will do so. The proper routing does become obvious when you give it a little thought, but a PO or mechanic in a hurry might have chosen an improper placement.
 

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I had a similar problem on the 94 I had. Where the wire harness came up around the neck the wire rubbed through and was popping my 30a breaker. Glad you got it fixed.
 
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