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Discussion Starter #1
Hey all,

So I'm new to the forum here but I just wanted to post this to see if anyone had any ideas.

I'm on a roadtrip from VA out to California and I've had an issue that's started on my 07 Vulcan 900 Custom (only mods have been full debaffle exhaust). Bike has 13K miles.

Starting in Colorado, I first noticed it two days ago as I was stopping for the night. I noticed it drops out at idle like it wants to die but it catches itself, at first it was only at idle. Now it is at all speeds. It stumbles every few seconds. It runs fine, no codes set, and no FI light

I've done a whole bunch of checks to try and figure it out but I'm stumped.

At first I noticed it mainly seemed to kick out when the air switching valve would click, so I bypassed that system. No change.

Then I saw someone mention possibly stator/RR. I tested voltage at the battery at idle and 3000 RPM. Consistent 13.9-14.0V no change. I just installed a new stator Rick's and RR before I left. I figured the lower voltage was because my solder joints were kind of crappy. Only thing that gets me is no increase of Voltage with higher RPM. The RR plug is dielectric greased to prevent corrosion.

Next I figured perhaps air. Checked the filter and operation of throttle body and subthrottle actuator. All normal.

Then I checked spark via a spark plug inline tester and swapped plugs. No change. For the record I'm running the NGK iridium CPR plugs. Just replaced them 2K ago.

Checked for bad gas by running two fresh tanks through it with some fuel system treatment because I thought perhaps bad gas. No change. Figured also if fuel pump/injector was faulty it would lose power. It has full power and I can run it all the way up to 90mph no problem.

I have no idea what's causing this and it's driving me up the wall. Please someone help, I have tools to work on it on the road but since I'm traveling in the middle of nowhere Utah ATM I'm worried it is going to die on me and leave me stranded.

Thanks for any help in advance.
 

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Have you tested the AC voltage the stator puts out to see if there is an issue there? Being a new stator and rr that should be fine I'm guessing tho.
 

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Discussion Starter #6
I just took it to an independent that a local guy recommended to get an opinion. He listened said it sounds like rear cylinder intermittent misfire. He thinks the spark plug cap itself. Says they unscrew from the coil wires and sometimes carbon tracks will cause a very intermittent misfire like what I'm experiencing. Thoughts? He's an ex Kawi dealer tech although I take that with a grain.
 

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I was thinking maybe a cracked insulator on a plug but this sounds plausible to me. You might see evidence of misfiring on a plug if you pulled them. It might be a bit dirtier. It is hard to tell from a forum. Good luck with it.

You might be able to pull or wiggle the plug wires while it is running and see if you can make it misfire.
 

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So sounds like the bike is fuel injected?
If it was my car I'd suspect one injector is bad.
Have had it happen a few times on different cars.
In the car it feels like a miss and the car will jerk.
 

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Discussion Starter #9
I got insulators coming, I have to pick them up out of California when I cross through LA. It's progressively getting worse.. instead of one miss every 5-10 seconds they're now spurts. Where it will be 2-3 seconds, 3-5 misses with a few milliseconds in between. And repeat the cycle. Kind of freaking me out since I'm traveling through Utah and Nevada but here's hoping it will get me to California. Checking the plugs shows a marginally darker rear plug but it does seem to me that it's missing on the front

Another note. The air switching valve is acting funny as well.

So if I rev it up and pull to a stop, after about 10 seconds the switching valve will go crazy and just constantly keep clicking every second or so. Then it stops when I rev it up to go again and repeat. My hypothesis is it's doing its job and trying to compensate for all the unburned fuel in the exhaust. Is this correct? Or part of the problem?
 

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Are you able to get a cheap rev meter just to connect to that rear plug. While it won't show the true revs it will show any misfires.

Normally just connecting the rev meter to the battery and winding the sensing wire around the suspected lead it should work. Some multi meters can even work but they cost a tad bit more than a cheap rev meter.
 

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Did you survive?
 

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Discussion Starter #17
The only thing I could think of is that if it was a plug it must have been internal. They looked great. Double checked for cracks. Also when I swapped them as a diagnostic test a few days prior it didn't stop the missing. So my assumption was a bad cap. But I just wonder if that's common actually.
 
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