RPMs that hang after a blip of/ or on release of the throttle are most often the result of the idle screw/stop being set too many turns in.

Setting the idle too high(often in a attempt to compensate for incorrect jetting or adjustment) opens the throttle plates(butterflies) and uncovers the transfer ports(the little holes in the bore of the carb located by the throttle plate). This results in more air and fuel causing the rev hang.

Google image of transfer ports on a carb(not a vulcan 500 carb)

Lower the idle by backing the idle adjustment screw/knob out and if needed adjust the mix screws as needed.

If you have a stock setup(intake & exhaust with factory jetting), You will likely find the mix screws will want to be around 3 turns +/- 1/2 turn. Proper idle speed is 1300rpm IIRC.

 

If the idle were set too high, it would never return to normal as the poster said it does.

Most times, idle hang is caused by a vacuum leak or mechanical bind.

 

2 1/2 turns out is just a starting point.Adjust slowly each side to were you get the fastest smoothest idle.Than set you idle to 1200 RPM.

 

You guy's responded so fast to my problem that I had to get out on the bike and use your suggestions before it started raining. flstffex you were right about the idle knob being turned in too far. Setting the pilot screws at 2-1/8 turns out is obviously in too far. I backed the screws out until I got a faster and better idle and then turned the idle knob back out. Now the throttle is responding well and I am also getting better low end response which is what I was looking for in the first place. Thank you for taking the time to post the picture of the carb because that helped me see what is going on. I was pretty sure it wasn't a vacuum leak or binding because the problem happened as soon as I touched the screws. I just needed help getting the adjustment back on track.
Well now that it is going to rain for the next 24 hours I might as well get to the Gym. Looking forward the riding again Friday.
Thanks again everyone for the suggestions.

 

You guy's responded so fast to my problem that I had to get out on the bike and use your suggestions before it started raining. flstffxe you were right about the idle knob being turned in too far. Setting the pilot screws at 2-1/8 turns out is obviously in too far. I backed the screws out until I got a faster and better idle and then turned the idle knob back out. Now the throttle is responding well and I am also getting better low end response which is what I was looking for in the first place. Thank you for taking the time to post the picture of the carb because that helped me see what is going on. I was pretty sure it wasn't a vacuum leak or binding because the problem happened as soon as I touched the screws. I just needed help getting the adjustment back on track.
Well now that it is going to rain for the next 24 hours I might as well get to the Gym. Looking forward the riding again Friday.
Thanks again everyone for the suggestions.

Thank you for the follow up on it, it is always nice to know the resolution to a problem that was posted.

Also glad I could point you in the right direction.

 

Hi guy's, I have a 03 Kawasaki Vulcan en500c. The bike was running fine when I bought it, but I ran it out of fuel one day and when I filled the tank back up it ran for about 10 mins and started flooding. I bought a rebuild kit and it ran after that for a little bit, but started flooding again. I have the air\fuel mixture screws out 2 1\2 turns out, not sure if that may have anything to do with it. The bike only has 1,900 miles on it. If anyone can help, I would be very thankful. Thanks

 

Hopefully this is where I was supposed to post?

 

Welcome!

Gently tap both carb fuel bowls with a rubber mallet or screwdriver handle and see if that helps.
Most likely float needle valve is stuck open causing overflooding. Debris/rust usually gets in there, especially if tank is pretty rusty inside. That repair kit came with new float needles and you installed them, right?
Fuel mix screw has nothing to do with flooding tho.

And to add:
Check petcock too, its vacuum operated so fuel shouldn't be flowing on RES and ON positions at all.

 

A small fuel filter can prevent expensive floodings.

 

Unfortunately this is an old post, but I'm having somewhat similar issues with new-to-me 2007 Vulcan 500. Mine actually will NOT run with the choke on and it takes 4-5 starts when cold to get it to stay running. I got it 2 weeks ago, dumped the 6 year old gas out of the tank, of course that didn't fix it, so I pulled the carbs and cleaned them by hand with B12. Bike was able to start and run after, but as stated above it doesn't like it when it hasn't been warmed up. I put 150 miles on it last weekend, but it isn't 100%, so I did some reading and saw that the pilot SCREW is supposed to be 2 1/8 turns out, so I pulled the carbs again and unscrewed the pilot JET 2 1/8 turns, now the bike won't even start. So now I've pulled the carbs for the 3rd time last night and put them in an ultrasonic cleaner that I bought from HF last night on the way home. Here's my big hang up, I don't see a pilot screw. I've attached a pic of one of the carbs and a pic of the parts diagram. Where the heck is 16014??? The pilot jet I unscrewed is 92064, which I'm assuming is supposed to be screwed all the way in, like it was when I pulled the carbs the first time. I feel like this is gonna be, super simple making me feel dumb, but I don't care at this point. I'm already tired of pulling the carbs.

And to the previous poster from 2 months ago, that is most likely a bad float valve. Expensive little suckers, but that is the #1 culprit on our dirtbikes.

 

Pilot screw is under the brass plug in front of the float bowl......the one with the long nipple......It has to be removed to a access the screw..Carefully drill almost the cap & remove it with a self threading screw.

 

Pilot screw is under the brass plug in front of the float bowl......It has to be removed to a access the screw..Carefully drill almost the cap & remove it with a self threading screw.

Wow! Ok, thank you very much. I don't feel stupid now, I never would have figured that out. Thank you

 

Ok, so Blaine what is under the other plug below the brass plug? I'm not gonna lie, I'm nervous about drilling into the wrong one given a new carb is $500.

 

Ok, I did some checking and it is NOT the brass plug as stated above, it is the silver plug for the pilot screw. I posted a pic to help others avoid similar issues. It is called a welch plug and you can lookup youtube videos to assist with removal.

 

You got it..I did say the one with the long nipple (you must of seen it before my edit)
...A good starting point is 2 1/2 turns out & than adjust with the bike warm for smoothest/fastest idle.....It helps to lower your idle speed while adjusting as its easier to hear changes.