One carb only - Kawasaki Vulcan 750 Forum : Kawasaki VN750 Forums
Carbs and Fuel System
From the gas tank to the carbs
All fuel system discussion

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post #1 of 18 (permalink) Old 04-22-2018, 09:51 AM Thread Starter
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One carb only

Got my bike out from winter storage. Started right up, idles fine. But when I give it gas or go to take off, it is cutting out bad and seems like only one carb is working. As soon as I give it the gas, the other carb comes in, and it runs fine. Going down the road at highway speeds the bike runs perfect. But every time I stop and take off, it does the same thing. Rode it several times like this thinking it might clear up, but nope. Used seafoam in it last year before storage and it worked fine. Any ideas ?

1985 VN700A
FYI :
Kawasaki introduced the 750 cc class Vulcan worldwide in 1985. Due to tariff restrictions in the United States on bikes over 700 cc imported from Japan, the initial US spec model was limited to 699 cc. The tariff was lifted in 1986 and the Vulcan went to 749cc.
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post #2 of 18 (permalink) Old 04-22-2018, 10:24 AM
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Originally Posted by Vulcanlover View Post
Got my bike out from winter storage. Started right up, idles fine. But when I give it gas or go to take off, it is cutting out bad and seems like only one carb is working. As soon as I give it the gas, the other carb comes in, and it runs fine. Going down the road at highway speeds the bike runs perfect. But every time I stop and take off, it does the same thing. Rode it several times like this thinking it might clear up, but nope. Used seafoam in it last year before storage and it worked fine. Any ideas ?
One pilot jet clogged solid.
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post #3 of 18 (permalink) Old 04-22-2018, 10:25 AM
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Clogged pilot jet. You can try some seafoam. I'd drain the float bowl and just fill it with straight Seafoam, let it sit a half hour, and tap the carb briskly with a screwdriver handle a few times to help loosen up what might be causing the blockage. Put some seafoam in the tank, and go for a ride.
If that doesn't do it, you might have to pull the carbs....
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post #4 of 18 (permalink) Old 04-22-2018, 10:56 AM
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Clogged pilot jet. You can try some seafoam. I'd drain the float bowl and just fill it with straight Seafoam, let it sit a half hour, and tap the carb briskly with a screwdriver handle a few times to help loosen up what might be causing the blockage. Put some seafoam in the tank, and go for a ride.
If that doesn't do it, you might have to pull the carbs....
I don't think it will work. Gas isn't flowing through the pilot, so seafoam won't either. It will loosen more stuff and make it free to flow everywhere else that isn't clogged already. Gas/seafoam sitting in the bowl, only cleans the bowl.

Save time, bite the bullet, and pull the carbs.

You can leave the cables on the carbs, and the carbs connected together. Cover the engine with a towel, and just clean the jets on each carb. A can of carb cleaner is a must to shoot through all the passages.

Castrol Super Clean is a good alternative for soaking jets if you don't have anything else. Acetone works too.

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__________________________________________________ ____________
Repair Manual: http://www.mediafire.com/file/mj7z81..._Catalogue.pdf

Owner's Manual: http://www.mediafire.com/file/nscb5f...ers+Manual.pdf

Last edited by Spockster; 04-22-2018 at 11:02 AM.
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post #5 of 18 (permalink) Old 04-22-2018, 01:57 PM Thread Starter
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Thanks

Thanks everyone ! I seafoamed the crap out of it last year, used a whole bottle and ran it awhile then let it set a week. Didn't help a bit, but did make my petcock leak Guess I will have to pull the carbs. Gonna do it right, a friend has a parts tank, pretty sure I can do this np. Thanks for the help, I figured it was a clogged Pilot jet but wanted to see if you guys agreed. Might just go ahead and pull the motor and replace the stator while I am at it, tired of not knowing if the battery will get me home, lol.

1985 VN700A
FYI :
Kawasaki introduced the 750 cc class Vulcan worldwide in 1985. Due to tariff restrictions in the United States on bikes over 700 cc imported from Japan, the initial US spec model was limited to 699 cc. The tariff was lifted in 1986 and the Vulcan went to 749cc.
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post #6 of 18 (permalink) Old 04-22-2018, 06:03 PM
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I thought the pilot jet, like the main jet, sat submerged in the float bowl. So filling it with seafoam would enter the jet. Perhaps I'm thinking of a different carburetor. ??

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post #7 of 18 (permalink) Old 04-22-2018, 06:50 PM Thread Starter
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No idea

I have no idea, never had a motorcycle carb apart in my life. Might be a chunk in it that the seafoam wont eat too. I will post what I find if I can see whats up with it before I tank it. Thanks for the help KM.

1985 VN700A
FYI :
Kawasaki introduced the 750 cc class Vulcan worldwide in 1985. Due to tariff restrictions in the United States on bikes over 700 cc imported from Japan, the initial US spec model was limited to 699 cc. The tariff was lifted in 1986 and the Vulcan went to 749cc.
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post #8 of 18 (permalink) Old 04-22-2018, 06:55 PM
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I thought the pilot jet, like the main jet, sat submerged in the float bowl. So filling it with seafoam would enter the jet. Perhaps I'm thinking of a different carburetor. ??

These carbs have a separate float chamber and jet chamber. While there is fuel in the jet chamber, it has to be drawn upward through the jets (as usual). If the jet is clogged up tight, cleaners can't do much.

Had to soak my pilot a couple of hours and poke a wire though it between soaks. Need a drill bit that size, but I stripped wire from a bread tie. Make sure you poke out the emulsion holes on the side of the jet.

Emulsion holes



Float Chamber



Jet Chamber


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__________________________________________________ ____________
Repair Manual: http://www.mediafire.com/file/mj7z81..._Catalogue.pdf

Owner's Manual: http://www.mediafire.com/file/nscb5f...ers+Manual.pdf

Last edited by Spockster; 04-22-2018 at 06:57 PM.
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post #9 of 18 (permalink) Old 04-23-2018, 09:18 AM
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Well if the jets do not sit in fuel when the bike is off, that likely explains the multitude of carb problems we've seen over the years.
Just about every motorcycle I've owned that was not fuel injected, never had any carb or fueling problems .....except for the Vulcan 750.

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post #10 of 18 (permalink) Old 04-23-2018, 09:39 AM
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Seems like it's always the rear carb that dries out in storage a few days, maybe because the direction it tilts, not sure.

So you evaporate the gas, and the residue that's left gets into the jets on the next ride.

Got to get the seafoam in there before a jet becomes clogged.

Don't believe we would have so much trouble if we had real gasoline.

Edit: The tip of the jets do sit in fuel, when the chamber is full. It just won't get pushed up through the jet by the weight of the fuel. The fuel gets drawn up by engine vacuum.

2003-21k mi
Shaved w/UniPK92+Stock Jets-TPE/MOSFET-Shinko Tires-AGM batt-bags-chrome-LEDs...more
__________________________________________________ ____________
Repair Manual: http://www.mediafire.com/file/mj7z81..._Catalogue.pdf

Owner's Manual: http://www.mediafire.com/file/nscb5f...ers+Manual.pdf

Last edited by Spockster; 04-23-2018 at 09:51 AM.
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