I really need help...this bike is killing me. - Kawasaki Vulcan 750 Forum : Kawasaki VN750 Forums
Carbs and Fuel System
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post #1 of 38 (permalink) Old 09-29-2011, 12:27 AM Thread Starter
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Exclamation I really need help...this bike is killing me.

Ok, I'm currently working on a 2001 VN750. As far as I can tell, everything is stock. Basically, the problem is that the bike is running extremely rich. Here's the rundown:

The bike backfires, though not so much as before I started working on it. I get black smoke from both exhausts when I roll on the throttle, though not ever singe time I rev it up. The smoke is accompanied by a strong gas smell...and once or twice I've witnessed a couple of fireballs out the exhaust. It gets considerably worse when it warms up, meaning its drive-able when I first start it up, but after a few miles I have to kinda stay on the throttle to keep it from choking out at stoplights. I realize that it probably isn't smart to drive it, I've only been driving it down the road and back in attempts to diagnose problems.

The carbs were cleaned by a bike shop in Lexington, KY. He took them apart a couple of times in an attempt to diagnose the problem. I had the carbs off 2 days ago, and took them apart myself to see if I could find anything he missed, but they looked clean and everything seemed in good shape. I did discover that there weren't hoses attached to the float chamber vents. I'm not sure if that's what you call them, but I'm referring to the two hoses that come off of the middle part of the carb assy and run to a T joint, which runs to the right side air filter box (all of which I learned on this site, so thanks!). I bought some 5/16 hose and a T joint and installed those when I put the carbs back on. After the install, I got a new symptom, which was that the bike lost all power under load, cutting out whenever I got it around 4000 rpms. I then tried capping that vent hose...and the bike ran great for the first time since I've had it. That lasted for about 15 miles, then it reverted back to its old state of running extremely rich and choking itself out.

When I put the carbs back on, I cleaned the spark plugs and reinstalled them. I removed them after the ride, and they were pitch black again. Based on the plugs, I'm pretty certain its rich on both cylinders. I've currently got the mixture screws at 2 1/4 turns, though I've had them from 1 1/2 to 3 turns in the last two weeks while trying to figure out whats going on, and I really can't tell much difference in the way the bike runs no matter what they're set at. I checked the numbers on the jets when I had the carbs apart, and they're factory size, unless the previous owner drilled them out or something, and I really don't know how to check that. I only know that the numbers on the jets were 132/38, which is what the repair manual calls for.

I've done tons of reading on this site in the past few months. The bike was purchased in May and was in a shop for 3 months, and all of that time I was reading on here trying to diagnose the problem, while also corresponding with the mechanic. I'm just kinda at wits end here guys, and I'd really appreciate anything anyone can suggest. I've replaced the whole ignition system pretty much, meaning the igniter box, the coils, the plugs, the plug wires and the plug wire connectors. The shop changed the choke plungers, cleaned the carbs, replaced the stator and the voltage regulator, along with a million other things. I don't know what other info to ad, but I'll answer any questions to the best of my abilities, I'll take pics, and I'll try to do whatever anyone can suggest, though at this point I've gotta try to stay cheap because I'm almost out of funds from working on this damn thing and paying the hefty bike shop bill.

I've considered doing an ear shave and rejetting to see if that has any effect, but I honestly don't even know if its fuel or air that's causing my problems. I really thought about ordering new float valves and pins, but it seems unlikely that they would both be bad, since it seems like its equally rich on both cylinders. That implies that the problem isn't just in one of the carbs, right? To give you an idea...I filled the bike up after I finished reinstalling everything, rode a little less than 50 miles, and now I've got a little over 1/4 tank of gas left. It's literally drinking fuel.

Thanks in advance, and I'm sorry this post is so long. I was trying to be as detailed as possible. And sorry again if I left out any necessary info.
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post #2 of 38 (permalink) Old 09-29-2011, 12:48 AM
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Gonna toss my penny in here if ya dont mind. Check the plugs and make sure they are the right ones for your bike.
Check to make sure the choke needle arms are all the way down in the body seats.
Check the left handle bar where choke lever is to make sure its letting the needle arms close all the way.
Check that the choke needles bodys threads are in snug & thight in the carbs.
Make sure these is not blockage of air passage ways to the carb inlets. This one got me once!
Make sure the two fuel bowl vents that tie into the "T" on top of the carbs are vented to the right air cleaner filter box with no kinks...
Cant hardly see BOTH carbs running RICH all the time. White smoke means fuel is burning, black smoke means oil is burning. Let us know whats ya find!!


Vulcan #1 1993 - 28K
Vulcan #2 1999 - 26k
It All Comes Down To 3 Things:
#1 Fuel
#2 Spark
#3 Mechanical
Any One Fails - Then It Dont Run

____________________________________

ANTICIPATED MODS:
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Last edited by OldHipWesTex; 09-29-2011 at 12:50 AM.
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post #3 of 38 (permalink) Old 09-29-2011, 12:48 AM
If only it had 6th gear..
 
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Because you say it's somewhat rideable when it's cold, the enricher plungers come to mind. Sticking broken, bent linkage, whatever. Then I think of float valve(s) not shutting off... more gas is needed when engine is cool but then not as much when it warms up. Floats not closing correctly - flooding after warm up. Good luck.

Dave

Mods:
Jetted, shaved & coastered
Home made under-tank single filter
Converted ACCT's to manual (thanks wib714)
Dual vac lines on petcock (my cure for ticking)
LED tail/plate lights
Relocated helmet lock to license plate

Added stuff:
Customized hard bags w/ lights
Chrome levers
Hellcat windscreen
LED running lights
Home made 'Vita-Volt' meter
Foot rests on engine guard
Tunes

Hmm....she was on the back when we left.... ??
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post #4 of 38 (permalink) Old 09-29-2011, 12:55 AM
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Oh Yeah,, What Dave Just Said Tooo


Vulcan #1 1993 - 28K
Vulcan #2 1999 - 26k
It All Comes Down To 3 Things:
#1 Fuel
#2 Spark
#3 Mechanical
Any One Fails - Then It Dont Run

____________________________________

ANTICIPATED MODS:
Build Fiberglass Fenders F/R
Mold & Cast New Turn Signals Lights
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post #5 of 38 (permalink) Old 09-29-2011, 01:04 AM
If only it had 6th gear..
 
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Quote:
Originally Posted by OldHipWesTex View Post
Oh Yeah,, What Dave Just Said Tooo
we both musta been brainstormin' at the same time and wrote pretty much the same stuff, ha ha. But yeah keep us updated, and no worries about being long. It's often the other way.. with not enough info and you gotta throw out scenarios and fish for more details to try and help the person asking. Take care.

Dave

Mods:
Jetted, shaved & coastered
Home made under-tank single filter
Converted ACCT's to manual (thanks wib714)
Dual vac lines on petcock (my cure for ticking)
LED tail/plate lights
Relocated helmet lock to license plate

Added stuff:
Customized hard bags w/ lights
Chrome levers
Hellcat windscreen
LED running lights
Home made 'Vita-Volt' meter
Foot rests on engine guard
Tunes

Hmm....she was on the back when we left.... ??
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post #6 of 38 (permalink) Old 09-29-2011, 01:13 AM
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Oh Yeah,, What Dave Just Said Tooo


Vulcan #1 1993 - 28K
Vulcan #2 1999 - 26k
It All Comes Down To 3 Things:
#1 Fuel
#2 Spark
#3 Mechanical
Any One Fails - Then It Dont Run

____________________________________

ANTICIPATED MODS:
Build Fiberglass Fenders F/R
Mold & Cast New Turn Signals Lights
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post #7 of 38 (permalink) Old 09-29-2011, 01:35 AM Thread Starter
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wow, thanks for the quick responses!

The plugs are NGK DPR7EA9, which I think I'm almost positive I've read on here is right. They're fouled, and I ordered new ones yesterday. I'm pretty much resigned to replacing them a couple of times in the process of getting her squared away, lol.

The choke plungers were changed at the local shop, and they appear to be seating fine. I was focused on those being the issue at one point so I kinda looked over all the stuff you mentioned with those. I tightened the choke needle body's, and the forks that pull them up and down look to be just right. When I work the choke lever open and closed, I can watch both of them moving up and down like (I think) they're suppose to.

The fuel bowl vents are indeed routed to the right air box, but I'm a little curious about how that hose goes into the air box. Basically, my right air box has an open square in the back of it, and I've just got the end of that hose laying in there. It kinda looks like its suppose to fit snug when I look at the repair manual. Am I missing something on that?

By carb inlets, are you referring to the boots coming from the surge tank? Sorry, I'm a newbie, but I'm trying to keep up! If so, what's the best way to check for blockage? I know I'm gonna end up pulling the carbs again soon, so I guess when I have the carbs off I can check that?

Black smoke means oil burning...that's bad, and I'm ashamed I didn't know that. I'm for sure getting black smoke.

Dave - I really had the same thought about the float valves, which is why I said I was seriously thinking about replacing them. I was telling a buddy the exact same thing today, and I'm pretty sure I'm gonna go ahead and order them this week, they aren't that expensive anyway. I did check the fuel level when I took the carbs apart, and I did that according to the directions in the service manual.

Lastly, I should have mentioned this earlier...the bike starts without any choke at all. So I never turn it on. I've checked it several times to ensure the plungers are closing accurately, but I don't actually "use" the chock, cause the bike never needs it. I'm guessing that's a bad thing though, right?

Hope I answered everything.
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post #8 of 38 (permalink) Old 09-29-2011, 02:02 AM
If only it had 6th gear..
 
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Just one correction on the smoke. Black is soot, carbon, too much fuel and blue is oil. White is usually either condensation, hot gas out of a cool exhaust, or when its a bad thing, a head gasket. I think you're on the right track though. I still think you got a stubborn float valve or seat causing this. One guy on here, Ceal, found the little spring pin on float valve wouldn't push in or out. He free'd it up and it fixed the problem. I think it was similar to yours.

Dave

Mods:
Jetted, shaved & coastered
Home made under-tank single filter
Converted ACCT's to manual (thanks wib714)
Dual vac lines on petcock (my cure for ticking)
LED tail/plate lights
Relocated helmet lock to license plate

Added stuff:
Customized hard bags w/ lights
Chrome levers
Hellcat windscreen
LED running lights
Home made 'Vita-Volt' meter
Foot rests on engine guard
Tunes

Hmm....she was on the back when we left.... ??
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post #9 of 38 (permalink) Old 09-29-2011, 02:08 AM Thread Starter
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Thanks so much man, I think that's gonna be the first thing I do. Any suggestions on where to buy the float valves?

Also, I hadn't mentioned this before cause I can't really even figure out how to describe it, but I have a question about the float valve seat, that the pin sets in when it closes. When looking at the seats on my carbs, I noticed that the seats each have two small holes. On one of the carbs, the seat is turned so that the holes are exposed, but on the other the seat is turned so that the holes are covered. Does that make sense, and should it be this way?

Rob
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post #10 of 38 (permalink) Old 09-29-2011, 02:20 AM
If only it had 6th gear..
 
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Quote:
Originally Posted by saintofkillers View Post
Thanks so much man, I think that's gonna be the first thing I do. Any suggestions on where to buy the float valves?

Also, I hadn't mentioned this before cause I can't really even figure out how to describe it, but I have a question about the float valve seat, that the pin sets in when it closes. When looking at the seats on my carbs, I noticed that the seats each have two small holes. On one of the carbs, the seat is turned so that the holes are exposed, but on the other the seat is turned so that the holes are covered. Does that make sense, and should it be this way?

Rob
Hmm.. I think Mine were like that but not totally sure. I remember pausing and thinking something was weird. Maybe take a pic if you take them apart again. Gotta sleep 'fore I fall apart. Ttyl.

Dave

Mods:
Jetted, shaved & coastered
Home made under-tank single filter
Converted ACCT's to manual (thanks wib714)
Dual vac lines on petcock (my cure for ticking)
LED tail/plate lights
Relocated helmet lock to license plate

Added stuff:
Customized hard bags w/ lights
Chrome levers
Hellcat windscreen
LED running lights
Home made 'Vita-Volt' meter
Foot rests on engine guard
Tunes

Hmm....she was on the back when we left.... ??
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