Carbs ??? - Kawasaki Vulcan 750 Forum : Kawasaki VN750 Forums
Carbs and Fuel System
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post #1 of 9 (permalink) Old 06-08-2019, 08:25 AM Thread Starter
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Carbs ???

Hey to all you carb guys. My problem started the other day while on a ride,my 91 running great,then at a stop sign it died,wouldn't idle. Started it up and keeping the revs up I made it home. I tried turning the idle knob,no difference. When running,I pulled the back cylinders plug wires,no difference. I changed out the plugs and it's now running on both cylinders but I have a hesitation when I open the throttle. It will rev up but it's not close to how it was running. Always ran some Seafoam through it,and never had any problems before. Any help will be greatly appreciated.
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post #2 of 9 (permalink) Old 06-08-2019, 09:55 AM
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Seems like a mix of two problems. I started out thinking clogged pilot jet, but the spark plugs threw a curve in there.

Still seems like a clogged pilot, and check the vacuum line on the petcock after you run it some, see if it's wet or dry. Flooding rear cylinder fouled those two plugs?

When mine had one clogged pilot, I had to crank the idle adjustment way, way up. It ran on one cylinder at low speed, then exploded with power when the main jet kicked in.

If you already had seafoam in the tank when this began, running it might clear it up, mine did that once during a ride, I ran about 15 miles pulling the choke halfway to get some speed, turning the choke off then holding full throttle and letting it bog until I needed to speed up again. Real PITA way to ride, but I was already 60 miles from home. I believe that time it was a clogged main jet.

Tearing the carbs down is the surest way to clean it out. I'm still half wondering about the ignition on the rear cylinder though.

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post #3 of 9 (permalink) Old 06-08-2019, 10:10 AM
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If your carbs are clean and you still get this weird stuff happening check your petcock. A tiny hole in the vacuum diaphragm can leak fuel into the vacuum line causing idle problems and all kinds of other performance issues.

Jim Favors
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post #4 of 9 (permalink) Old 06-14-2019, 08:29 PM Thread Starter
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Thanks for the imput guys. My tank was low on gas so I put in a couple ounces of Seafoam in it,left the petcock open .Then I pulled the plugs ,back cylinder plugs were wet. Put in some old plugs that were in good shape until I could get some NGK Iridiums. Bike started,running on both cylinders now but still wouldn't idle. Kept starting it trying to run the Seafoam through it,pilot jet ??? Then on the 3rd day just like you said,bang started reving up and running like it should. Idle screw was turned way up so I backed off and it was idling nice. Today took it out and let the tongue hang out and she ran beautiful. Must have been clogged jet like you said,but still wondering about the wet plugs. Tomorrow I'll pull them to inspect and perhaps check my air filters. Haven't in a while. Was dreading taking the carbs off,looks like maybe I dodged a bullet. Thanks again.
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post #5 of 9 (permalink) Old 06-16-2019, 11:04 AM
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Back plugs were wet after sitting overnight, before any cranking? I'm thinking stuck float on that cylinder, but the seafoam cleared that too maybe? Otherwise the plugs couldn't get wet without cranking.

Make sure the vacuum line to the petcock stays dry. (front cylinder)

2003-21k mi
Shaved w/UniPK92+Stock Jets-TPE/MOSFET-Shinko Tires-AGM batt-bags-chrome-LEDs...more
__________________________________________________ ____________
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Owner's Manual: http://www.mediafire.com/file/nscb5f...ers+Manual.pdf
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post #6 of 9 (permalink) Old 06-17-2019, 02:48 PM Thread Starter
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Hey Spockster,today was the first day I could work on it,been raining. So I got my Iridiums all cleaned up,gapped. Took out the plugs that only been in for 50 miles or so,not quite running as good as I first thought. Still 2 were a little wet. Put in the Iridiums. Then remember I told you that I haven't checked the stock air filters in a while?? Took off the left one,fine little dirty,then took off the right one and a nice sized mouse nest came falling out. I immediately started laughing,thinking there it is,the cause of it all. Took some pics,will try to post them if I remember how. Someone up there is really looking out.for me.
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post #7 of 9 (permalink) Old 06-17-2019, 02:55 PM Thread Starter
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Looks like the pics went through. Do you think this would cause d some trouble,lol. Took itfor a ride and she ran like a bat out of hell. Went through the gears 2 up,0 to 75.very guick,faster then my 03,felt like it anyway. Not bad.for a 28 year old bike. Now I can finally work on that front end noise I posted about on my 03. Put it on the stand and.side to side play,bad bearings. So thanks buddy for all you do man. Have to send you a PM about something you recommend ed to me once. Can't recall.....
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post #8 of 9 (permalink) Old 06-17-2019, 03:25 PM
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Quote:
Originally Posted by Paulywog View Post
Hey Spockster,today was the first day I could work on it,been raining. So I got my Iridiums all cleaned up,gapped. Took out the plugs that only been in for 50 miles or so,not quite running as good as I first thought. Still 2 were a little wet. Put in the Iridiums. Then remember I told you that I haven't checked the stock air filters in a while?? Took off the left one,fine little dirty,then took off the right one and a nice sized mouse nest came falling out. I immediately started laughing,thinking there it is,the cause of it all. Took some pics,will try to post them if I remember how. Someone up there is really looking out.for me.
Wow! Yep, that will do it. That rotten foam by itself can get sucked into the airbox and carbs, it's been found in there.

You're welcome, shoot me a PM, I already know what you're talking about.
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2003-21k mi
Shaved w/UniPK92+Stock Jets-TPE/MOSFET-Shinko Tires-AGM batt-bags-chrome-LEDs...more
__________________________________________________ ____________
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Owner's Manual: http://www.mediafire.com/file/nscb5f...ers+Manual.pdf
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post #9 of 9 (permalink) Old 06-18-2019, 10:25 PM
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That could definitely do it. Nice to see oem air cleaners. As for cleaning the carbs, I wouldn't ever remove them if I didn't have to. I don't think that Seafoam in the gas will do any good. I drain the float bowls occasionally, and fill the carbs with full strength Seafoam through the carb vent hose, behind the right filter housing. Pour it very slowly, and stop when it starts coming out the carb float bowl overflow. If you put too much, it can run into the cylinders. Let it soak for a couple days.

I am a motorcyclist, NOT a biker.


1997 Vulcan 750, purchased about a week ago
2006 Sportster 1200 Low
2013 Royal Enfield Bullet 500, converted to carb
2001 Yamaha XT225, heavily modified
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