Carbs are spotless but still only runs on choke - Kawasaki Vulcan 750 Forum : Kawasaki VN750 Forums
Carbs and Fuel System
From the gas tank to the carbs
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post #1 of 9 (permalink) Old 03-17-2019, 04:52 PM Thread Starter
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Carbs are spotless but still only runs on choke

Hello Vulcan heads on this wonderful Sunday afternoon. Got some issues to see if you guys can help me out. Took carbs apart because bike only ran on choke and I couldnt rev it without it dropping rpms, cleaned everything (float needles, float chamber, diaphragms, ect) even though it didnt look like barely anything needed to be touched and put it all back together today (jets are fantastic but still cleaned and blew and cleaned again). Well I can rev it sometimes with it working properly and others not so much. I set the mixture screws at 2 1/2 turns and the idle adjust is backed off. Had to recap the right vaccuum line on the right carb. Im trying figure out what would the the next step be?
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post #2 of 9 (permalink) Old 03-17-2019, 05:41 PM
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Originally Posted by K2unit3d View Post
Hello Vulcan heads on this wonderful Sunday afternoon. Got some issues to see if you guys can help me out. Took carbs apart because bike only ran on choke and I couldnt rev it without it dropping rpms, cleaned everything (float needles, float chamber, diaphragms, ect) even though it didnt look like barely anything needed to be touched and put it all back together today (jets are fantastic but still cleaned and blew and cleaned again). Well I can rev it sometimes with it working properly and others not so much. I set the mixture screws at 2 1/2 turns and the idle adjust is backed off. Had to recap the right vaccuum line on the right carb. Im trying figure out what would the the next step be?
i had issues with the carb boots not seating correctly (my fault) and having a vacuum leak. make sure the boots are clocked appropriately and the clamps tightened down well. Since i have a set of jets in my hand, it looks like your carb doesn't have any in it. Were the pictures taken without jets in them?

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post #3 of 9 (permalink) Old 03-18-2019, 12:22 AM Thread Starter
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Originally Posted by TheJabberWoggy View Post
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Originally Posted by K2unit3d View Post
Hello Vulcan heads on this wonderful Sunday afternoon. Got some issues to see if you guys can help me out. Took carbs apart because bike only ran on choke and I couldnt rev it without it dropping rpms, cleaned everything (float needles, float chamber, diaphragms, ect) even though it didnt look like barely anything needed to be touched and put it all back together today (jets are fantastic but still cleaned and blew and cleaned again). Well I can rev it sometimes with it working properly and others not so much. I set the mixture screws at 2 1/2 turns and the idle adjust is backed off. Had to recap the right vaccuum line on the right carb. Im trying figure out what would the the next step be?
i had issues with the carb boots not seating correctly (my fault) and having a vacuum leak. make sure the boots are clocked appropriately and the clamps tightened down well. Since i have a set of jets in my hand, it looks like your carb doesn't have any in it. Were the pictures taken without jets in them?
That may be it...Sound like somethings a lil off like I can hear gasps of wind at the right carb...Ill check that tomorrow...I had them out when I took the pic lol...But I can assure you they are back in right now...Hopefully thats my issue as I noticed a nipple on the underside my gas tank but no hose for it...Ive learned a ton in the last few weeks lol...Btw thanks for your assistance so far...I really appreciate it

*UPDATE*

Didnt really get a chance to touch it until yesterday. I took the carbs out again, this time in about 40 mins. Really excited about that as the whole process took me 6 1/2-7 hours the first time. I reseated the rear boot and matched the humps on the cyliner and the boot. Still I hear this gasping. Maybe its coming from the right vacuum hose as it is a short plugged piece. The hose I replaced was a longer plugged one. Might need to try and find the emission valve under the seat for it to go into. PO seemed like he was going to do the ear shave mod but stopped halfway. Also now I cant even get it to turn over even with choke fully on. Battery full, gas in tank. There was a hose that ran from the middle of the airboxes(pics attached you can see the clamp) that I attached to the T on the carbs thinking that was how it was supposed to be. Well a differtent hose comes from the T and goes into the airbox(fixed). I read that the hose between airboxes just hangs in deadspace(fixed) but the bike wont start now. Maybe Its a combo of things. Forgot to mention I also I backed the mix screws off another half so Im at 3 turns now. That may have some to do with it as well
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Last edited by K2unit3d; 03-24-2019 at 08:33 AM.
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post #4 of 9 (permalink) Old 03-23-2019, 10:44 AM
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That may be it...Sound like somethings a lil off like I can hear gasps of wind at the right carb...Ill check that tomorrow...I had them out when I took the pic lol...But I can assure you they are back in right now...Hopefully thats my issue as I noticed a nipple on the underside my gas tank but no hose for it...Ive learned a ton in the last few weeks lol...Btw thanks for your assistance so far...I really appreciate it
A nipple under the gas tank, like, all the way under? Like by the fuel level sender connection? I believe that's a drain just in case the fuel level sender unit leaks. The parts catalog doesn't show a hose, but you can put one on there to direct leaking gas someplace other than directly onto the engine. I don't have a hose on there.

Another nipple on the gas tank is at the back of the tank. I want to say that is a drain in case you over fill the tank and a vent so air can get into the tank so providing fuel to the carbs doesn't create a vacuum inside the tank. It's also for fuel emissions if you have those parts. That hose on mine is like 14" long and runs straight down between the battery and engine and behind the transmission.

1995 VN750
Ear Shave Mod
2-Wire Mod
Blue Wire Mod
RLU Bypass
SH847 R/R
Degoat
V&H Pipes
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post #5 of 9 (permalink) Old 03-24-2019, 08:31 AM Thread Starter
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Originally Posted by TheJabberWoggy View Post
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Originally Posted by K2unit3d View Post
That may be it...Sound like somethings a lil off like I can hear gasps of wind at the right carb...Ill check that tomorrow...I had them out when I took the pic lol...But I can assure you they are back in right now...Hopefully thats my issue as I noticed a nipple on the underside my gas tank but no hose for it...Ive learned a ton in the last few weeks lol...Btw thanks for your assistance so far...I really appreciate it
A nipple under the gas tank, like, all the way under? Like by the fuel level sender connection? I believe that's a drain just in case the fuel level sender unit leaks. The parts catalog doesn't show a hose, but you can put one on there to direct leaking gas someplace other than directly onto the engine. I don't have a hose on there.

Another nipple on the gas tank is at the back of the tank. I want to say that is a drain in case you over fill the tank and a vent so air can get into the tank so providing fuel to the carbs doesn't create a vacuum inside the tank. It's also for fuel emissions if you have those parts. That hose on mine is like 14" long and runs straight down between the battery and engine and behind the transmission.
Mine is almost right smack dab in the middle and I dont know if it has to do with my bike not running right. I looked and I couldnt find anything.

Lol I dont even have the back one. Im just trying to figure out what I need at this point. I attached a pic of the nipple I have. Btw appreciate your help
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post #6 of 9 (permalink) Old 04-22-2019, 02:01 AM
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That nipple is one that “isn’t used”. Currently it is a spot we tend to use when an ear shave is done and you attach the vacuum line that went from the carb to the right side air filter box to that nipple.
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post #7 of 9 (permalink) Old 04-22-2019, 02:05 AM
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Additionally when I had a similar issue when I first received my bike it had been sitting outside under a tarp for awhile. I found that the vacuum line coming from the right side of the carb that goes to nothing that I’m guessing is a vent of sorts itself on the carb was packed by mud daubers wasps. Once it was cleaned out I didn’t have to use the choke anymore.
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post #8 of 9 (permalink) Old 04-25-2019, 01:27 AM
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At the rear of the gas tank there are either one or 2 nipples, depending on whether it is a CA model or not. They have 2. Nothing needs to be attached to either one for it to run properly, but if you have the CA model, the hose that connected to one of them needs to be plugged. I have a CA model (two of them now) and I just removed all the CA emissions crap and connected a hose to each one, and ran it down under the bike. Gas will come out of one of them if you fill the gas tank really full. There is a vacuum fitting on the right side carb that a small hose attaches to. That hose goes to the AIR system, another piece of emission crap that I removed. If the hose is there you can hook it up, or you can just cap the nipple on the carb. You should not hear any hissing sounds from anywhere. The way I look for vacuum leaks is to take an unlit propane torch, open it up just a little, and move it around any place where a vacuum leak might be. If the engine idle suddenly increases, you found a vacuum leak.

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post #9 of 9 (permalink) Old 04-25-2019, 06:07 PM
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Sliders?

Did you check the sliders. Mine got stuck once and I had the same symptoms. I disconnected the air cleaner tube and slid it up with my finger. I felt a little resistance, like there was grit or something in there, and just like that it was fixed.
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