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Richmond, VA
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26 Posts
Discussion Starter · #1 ·
The problem is this, the bike can be running fine for quite a while. Then suddenly it is as if all power is cut. This happens for a couple of seconds at most. Then the rear cylinder begins to fire and the bike runs on one cylinder. While riding on one cylinder, intermittently the front cylinder will start to fire, and then dies. Once it actually resumed firing for several minutes only to stop once again before I got home. While riding with one cylinder, on occasion the bike will lose all power momentarily then resume firing on the rear cylinder. It ALWAYS starts with both cylinders running. It seems to only cut out after riding 20 minutes or more.
On a rare occasion, within a minute or two after starting to ride, there will be a blip where it feels like the power is cut; not even for a second. Then it goes on running for about 20 minutes and does the cycle described.
I checked the wiring under the gas tank and the connections. I checked the ground cable. I checked the connections under the battery. I replaced the front Ignition Coil. I checked the fuses. I even have a new battery. Same thing keeps happening.

HELLLLLLLLLLLP!
 

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Prowling Tiger
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2,048 Posts
First thing I'd look at would be the ignition switch. Take the bike out again and when it starts acting up, jiggle the key. IF the symptoms improve, then remove ignition switch and clean it up. Otherwise, the problem could be stemming from somewhere else.

Does the problem arise when the bike has less than half a tank of gas? If so, then search for POOG's.

Others will chime in soon to provide an opinion.

Good luck.
 

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I'm thinking that the ignition swith would cut all power. do the lights remain on when this happens?

It sounds like a possible fuel issue....or lack of fuel....clogged jets maybe??

It also could be a thermal issue causing the electrics to fail. Check the 12V input connections to the coils to make sure they are clean and tight.
 

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Richmond, VA
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26 Posts
Discussion Starter · #4 ·
Ignition switch?

I am losing one cylinder consistently. The other generally runs fine. I made it back 40 miles on one cylinder. I do not understand how it can possibly be the ignition switch!?
 

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Richmond, VA
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26 Posts
Discussion Starter · #5 ·
Replaced boot on carbs months ago so fuel problem is doubtful. This seems to be electrical and possibly a short somewhere but I cannot find any breaks in the wiring harness. A key factor I believe is that the front cylinder only dies after running for a while. When it cools down it runs fine again.
 

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Prowling Tiger
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2,048 Posts
I am losing one cylinder consistently. The other generally runs fine. I made it back 40 miles on one cylinder. I do not understand how it can possibly be the ignition switch!?
I'd say disconnect the fuel lines from the petcock and point the nipples down. Take a small hose and suck on the vacuum. See if both sides are flowing fuel properly.

Have you ran any seafoam lately? Could be gunk gumming up the floats and or needles.

Have you checked for spark on the one cylinder? Take out the plug and ground it to the engine while attached to plug wire.

I am certain there are other causes for your problem. As you can tell, one problem can have many solutions.
 

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Premium Member
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1,803 Posts
Check the air gap on your pickup coils. They should be set around .020-.024 gap, (search pickup coil modification ) One or both may be way off.
 

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Richmond, VA
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26 Posts
Discussion Starter · #8 ·
BTW...
The tach stops working every time the front cylinder shuts down. It resumes each time the front cylinder resumes running.
 

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unless you tore the carbs apart for cleaning, they could still have debris in the jets clogging them.

Is your tank clean? any rust inside that could make it's way to the jets?

how do the plugs look?
are the front plugs running lean? or wet with fuel?
how does it compare to the rear plugs.
 

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BTW...
The tach stops working every time the front cylinder shuts down. It resumes each time the front cylinder resumes running.
tach runs of the electrical signal on the front coil.

Check your connections to the coil...the 12v connection could be dirty or loose.....no 12V will not allow it to fire.
 

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This sounds to me like and electrical issue especially since the tach is involved. Seems to me that there may be a loose ground somewhere in the ignition circuit.
 

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This sounds to me like and electrical issue especially since the tach is involved. Seems to me that there may be a loose ground somewhere in the ignition circuit.
agreed! was thinking fuel till he mentioned tach not working when front jug drops out.

It is either a loose or dirty connection to the coil, or some other thermal related issue in the ignition circuit controlling the spark.

"Check the air gap on your pickup coils. They should be set around .020-.024 gap, (search pickup coil modification ) One or both may be way off. "

Gapping the pickups won't really do much to help this issue as that is just a control signal to the ignition circuit. doing the mod might get you a stronger signal, but it also slightly changes the timing. I would find out what is causing the front coil to drop out first. Check all your wires going to the coil and the grounds...ALL the grounds including the chassis ground on the battery box......that will most likely take care of the tach not working as well.
 

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Def electrical IMO as others have said...my front cyl stops firing/misfires when the oil level in the crank is too high (covers the lower pickup coil)...also, if you still have the "goats belly", its awful close to many critical wires and can melt the insulation "just enough" to cause shorts, etc...remove the left side cover, and trace all the wires from the left hand engine cover all the way to the harness....check for pinches or melting...even the slightest...after that, check EVERY ground wire the bike has (this will take awhile, so many of em)...hope this helps...
 

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Gapping the pickups won't really do much to help this issue as that is just a control signal to the ignition circuit. doing the mod might get you a stronger signal, but it also slightly changes the timing. "
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My point exactly. He has an ignition problem. The bike starts and runs fine until it gets hot. When it cools down it is good again. If he had a bad ignition coil or coils the bike wouldn't start or would have very weak ignition. Generally the coil would not fail when hot but be good when cold. I still would check the pick up coils to see that they are gapped the same, within spec, and that the wiring is good.
 

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Check the plug wires where they hook up to the coil. The rubber on mine was stretched a little bit so the part that punctures the electrical wire was not making a good connection. Trim the rubber back to where it is flush with the wire and hopefully that will help you. Worked like a champ for me.
 
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