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Discussion Starter #1
Hi Guys,

I bought a 1996 VN1500 a few weeks ago and am loving it with one or two exceptions. I get a considerable amount of popping on deceleration which I know should mean a fuel/air mix problem. I pulled all the plugs and they were black so I replaced them all. I adjusted the fuel/air screw to 2 turns out and no change, so now I'm at 1 turn out and still doesn't seem to help.

To add to this problem, I seem to have no power at mid range RPMs. At lower RPM, it feels fine, but if I try to accelerate slow and smooth, it lags and sputters a bit. If I give it a lot of throttle, it kicks in and does fine for a fast acceleration.

A little back story on the bike...it only has 5700 miles on it! The guy I bought it from said he rode only a few times a year and that was mainly to church and back.

Does all this sound like a rejet, a carb remove and clean? I tried sea-foam and only put premium gas in. I've ridden approx. 200 miles since I had it. Any suggestions are certainly welcome.

Thanks,

Bill
 

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If it has power in the low end but not the mid, you might have too large a main jet or your needle might be too high. Do you know if it was rejetted? Your pilot circuit governs mostly the first 1/4 to 1/3 of your throttle range, so you might want to turn it back out to 2.5 turns. If your main is too big, or your needle too high, you might be getting too much fuel which can bog it down some. Since you said your plugs were sooty, that is a clue. I'd start with the needle, since it governs mostly the mid range of the throttle power band.

Here is some helpful info/

http://www.dansmc.com/carbs2.htm
 

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Discussion Starter #4 (Edited)
The guy I bought it from said it had been rejetted for the pipes but always had the pops. He also told me that it was worse when he pulled out the baffles (which by the way are back in.) I got it to the point where it is great on startup with choke on, great until the bike is warm with the choke off. Then, when the bike is warm, the popping begins at idle and on decel. I'm guessing that I'd have to remove the carb and disassemble to get to the needle?
 

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Sounds like he didn't marble or remove the reed valves. Reed valve allow air into the exhaust headers to burn off excess fuel gases and is part of the smog crap. Here's how to do it on a 900; the 1500 has the hose on the left side that goes into the air box, Block off this hose with A marble or wire nut and the popping should stop.
 

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Discussion Starter #6
But if the plugs are fouled and black, would that have something to do with the reed valve also, or do I have two separate issues.

Can I access the main jet without pulling the carb?
 

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Discussion Starter #7
If it has power in the low end but not the mid, you might have too large a main jet or your needle might be too high. Do you know if it was rejetted? Your pilot circuit governs mostly the first 1/4 to 1/3 of your throttle range, so you might want to turn it back out to 2.5 turns. If your main is too big, or your needle too high, you might be getting too much fuel which can bog it down some. Since you said your plugs were sooty, that is a clue. I'd start with the needle, since it governs mostly the mid range of the throttle power band.

Here is some helpful info/

http://www.dansmc.com/carbs2.htm
After reading this page, it seems as though I need some adjustment on my needle to lean out the mixture because of where I'm getting the lag with the throttle. Correct me if I'm wrong but for a lower mid range RPM, it's not the main jet that's the problem because when i pull on the throttle a bunch, it smooths out and runs fine.
 

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Sounds like the needle might need to go down a notch
 

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Yes. It's easiest if you pull the tank first. You can then unscrew the clamp holding the carb to the intake, remove the fuel line from the carb, and remove the screw holding the linkage to the carb. You can then pull the carb out far enough to where you can leave the linkage attached and don't need to remove it completely from the bike.

Here's a good how-to

http://www.vroc.org/faq/carb/carb-howto.html
 

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Discussion Starter #11
Ok,

Here's an update. I pulled the tank today (not too bad) and exposed 2 K&N air filters. They looked pretty clean but I wonder how they get good clean air when they're jammed under the tank?! Anyway, while I had the tank off, I noticed a tube between that was connected somewhere under the seat but not connected to anything else. It had a hose clamp and some sort of metal disc in the end of it. The metal disc had a small hole in it. Any idea what this might be?

Also, right after I started it up, I ran my hand down the exhaust pipes and noticed that both of them are puffing air where the header pipe meets the muffler pipe. No noticeable puff where the header meets the cylinder though. Could this be causing some of the popping?

One more thing, since this bike has dual carbs, it would also have dual air/fuel mix screws, right? The left side carb seems to have a fuel screw and the right side is a little more forward in the bike seems to have air adjustment. This comes from watching some youtube vids that said if the screw is on the air filter side of the carb, then it regulates air and on the cylinder side of the carb, then it regulates fuel.

Please excuse my many similar questions but I really an just starting out learning and and hungry for knowledge. Thanks a bunch.

Bill
 

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Bill, With the bike being a 96 and only having 5700 miles on it means it sat a lot. I think a good carb cleaning is in order regardless if this is the root of your popping or not. Taking carbs apart is a daunting task for a lot of folks, but really if you take your time and give yourself a good work space it's not that difficult. While you're in there, it will give you an opportunity to see where the needle is set and perhaps adjust. You can also take note of what jet sizes you're running. If you do decide to clean the carbs, make sure you set the floats to factory spec and get them both the same. If you don't have a tool to sync your carbs when you're done, it's a very good idea to bench sync them as close as possible while they're off. You want to get the throttle plates in exactly the same position as close as possible. Post back if you have any questions.
 

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Ok,

Here's an update. I pulled the tank today (not too bad) and exposed 2 K&N air filters. They looked pretty clean but I wonder how they get good clean air when they're jammed under the tank?! Anyway, while I had the tank off, I noticed a tube between that was connected somewhere under the seat but not connected to anything else. It had a hose clamp and some sort of metal disc in the end of it. The metal disc had a small hole in it. Any idea what this might be?

Also, right after I started it up, I ran my hand down the exhaust pipes and noticed that both of them are puffing air where the header pipe meets the muffler pipe. No noticeable puff where the header meets the cylinder though. Could this be causing some of the popping?

One more thing, since this bike has dual carbs, it would also have dual air/fuel mix screws, right? The left side carb seems to have a fuel screw and the right side is a little more forward in the bike seems to have air adjustment. This comes from watching some youtube vids that said if the screw is on the air filter side of the carb, then it regulates air and on the cylinder side of the carb, then it regulates fuel.

Please excuse my many similar questions but I really an just starting out learning and and hungry for knowledge. Thanks a bunch.

Bill
I was under the impression you had a 1996 1500 Classic, not the twin carb A model. They are different bikes. In 1996, they switched to the single carb Classic, but still made twin carb bikes for 1996 and 1997.

Sounds like the PO did an "ear shave" on it and ran the filters under the tank. That should work fine, but as Rick indicated, twin carb bikes can be a real bear to tune if they have been altered. I agree, they need to be torn down and cleaned. If it's too big a job for you, you can take the carbs down to a shop where they can be dip cleaned. My local shop charged me 30 bucks for a dip cleaning on my single carb.

Also be advised that the cylinders on a twin carb each have their own size jets, with one being smaller than the other.
 

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Also be advised that the cylinders on a twin carb each have their own size jets, with one being smaller than the other.
Weird. I never new that. I do love the simplicity of a single carb bike.
 

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Discussion Starter #15
I was under the impression you had a 1996 1500 Classic, not the twin carb A model. They are different bikes. In 1996, they switched to the single carb Classic, but still made twin carb bikes for 1996 and 1997.

Sounds like the PO did an "ear shave" on it and ran the filters under the tank. That should work fine, but as Rick indicated, twin carb bikes can be a real bear to tune if they have been altered. I agree, they need to be torn down and cleaned. If it's too big a job for you, you can take the carbs down to a shop where they can be dip cleaned. My local shop charged me 30 bucks for a dip cleaning on my single carb.

Also be advised that the cylinders on a twin carb each have their own size jets, with one being smaller than the other.
What is an "Ear Shave"? Also, the manual that came with it shows that it is the "L" model, not the "A." Anyway, I made an appt. today with a local shop and am taking it in tomorrow. I tried to tighten the pipe clamps around the exhaust leak but to no avail. Also, when I smelled the air puffing out from between the header pipe and muffler pipe, it smelled like gas. I'm pretty certain I'd be in over my head and it's the summer so I want to ride and not fix my bike! I'll take it to the professionals and have them fix it!

Thanks for all the responses.
 

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What is an "Ear Shave"? Also, the manual that came with it shows that it is the "L" model, not the "A." Anyway, I made an appt. today with a local shop and am taking it in tomorrow. I tried to tighten the pipe clamps around the exhaust leak but to no avail. Also, when I smelled the air puffing out from between the header pipe and muffler pipe, it smelled like gas. I'm pretty certain I'd be in over my head and it's the summer so I want to ride and not fix my bike! I'll take it to the professionals and have them fix it!

Thanks for all the responses.
The A,B,C an L models are all twin carb 1500s that look basically like this:



The 1500 D came out in 1996 as well, with the new classic stying, a single carb, and a 4 speed transmission.



An "ear shave" is where they remove the twin air filters, often called "ears", from the frame mount of the A-L models and put the filters under the tank.

 

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What is an "Ear Shave"? Also, the manual that came with it shows that it is the "L" model, not the "A." Anyway, I made an appt. today with a local shop and am taking it in tomorrow. I tried to tighten the pipe clamps around the exhaust leak but to no avail. Also, when I smelled the air puffing out from between the header pipe and muffler pipe, it smelled like gas. I'm pretty certain I'd be in over my head and it's the summer so I want to ride and not fix my bike! I'll take it to the professionals and have them fix it!

Thanks for all the responses.
The A,B,C an L models are all twin carb 1500s that look basically like this:





The 1500 D came out in 1996 as well, with the new classic stying, a single carb, and a 4 speed transmission.



An "ear shave" is where they remove the twin air filters, often called "ears", from the frame mount of the A-L models and put the filters under the tank.



This may be confusing, but it's the best explanations I've found yet:

2. What do A/B/C mean in relation to the 1500?

2.1. The A/B series of 1500 Vulcans were first manufactured in 1987 (VN1500A1/B1). The A series continued manufacture through the A13 in 1999, the last year the A was manufactured. The B6 appears in the service manual through 1992, but appears to only have been sold in the U.S.A. through 1990(B4).

The C series (C3 and C4, 1996 and 1997 respectively) were sold in the US for a relatively short time.

The A/B/C are essentially the same bike having Kawasaki twin carburetors, and a V-Twin engine. The B series is much like the A except for its wire spoke wheels, ROUND air intake covers, smaller (3.2 gallon) gas tank, and larger main jets. A’s have oval shaped air intake covers and 4.2 gallon tank. The B’s rear fender sweeps up and out while the A’s curves down following the rear tire lines.

The C is similar to an A with the addition of wire wheels, different stock handle bars (one piece drag style), and gold "wings" on the Vulcan gas tank emblem. Any mention of the 1500L model name (again, similar to the 88 and 88SE) should be taken to mean the C series Vulcan. It is sometimes called the "L".
http://www.oocities.org/manj01/faq.htm#1._What’s_a_BUBF?
 
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