A New Beginning - Still Having Problems - Kawasaki Vulcan 750 Forum : Kawasaki VN750 Forums
Carbs and Fuel System
From the gas tank to the carbs
All fuel system discussion

LinkBack Thread Tools Display Modes
post #1 of 6 (permalink) Old 07-31-2009, 04:53 AM Thread Starter
Join Date: Jun 2009
Posts: 49
iTrader: (0)
A New Beginning - Still Having Problems

Luckily I haven't spent a TON of money but the problems are still there. I'm going to start all over and follow everyone suggestions to a T.

Bike starts fine from cold. Using the choke I lose RPMs. Bike will not idle. Wants to gently die. I up the idle and pretty soon it's idling VERY high and I put it back to normal - then it wants to gently die again - I can't find the balance. Bike drives fine for a while - plenty of power. If I take a short ride and park it then start it up again shortly after it seems to still run ok. If I'm out for... 10ish minutes the bike will starts to sputter in RPMs. Seems like after 3000 it's all over the dial and I have to rev it to 5+ and ease the clutch in to make it run normal. Minimal backfire/misses (can't tell the difference). Sometimes when I pull the clutch in I see the RPM SHOOT down and ALMOST die if it weren't for my last minute throttle. I also notice that it will idle at 500RPM but I never let it idle long because I know it will die. After I cut then engine then try to restart around this time it's usually MUCH more difficult to start - I have to open the throttle quite a bit and it just barely turns over. At this point the choke MAY give more RPMs than normal (depending on where my idle screw is I guess). The bike still will not idle at this point. I get discouraged - I drive it home. And normally after a few rides with this typical pattern the battery will run itself out. Man... I DO NOT want to admit defeat!

Heres What I've Done:
-New petcock kit
-Cleaned Carbs twice
-Replaced Side Diaphragms for Carb
-Synched the carbs (using handmade manometer and regular motor oil - adjusting as I went on the road thinking that would help - god knows where it's at now)
-Air Screws Out 3x 360deg
-Vent Hose attached to Right ear Upper Side
-New Vacuum Hose to the Petcock
-Carb Dryer
-Engine Flush
-New Oil/Filter
-New Coolant

I'm ready to rock - I'll do anything.

Last edited by SyntaxJO; 07-31-2009 at 05:00 AM.
SyntaxJO is offline  
Sponsored Links
post #2 of 6 (permalink) Old 07-31-2009, 07:53 AM
Senior Member
one2's Avatar
Join Date: Mar 2008
Location: Iron County Missouri
Posts: 135
iTrader: (0)
I don't know much about this, but maybe you have a weak ground from the battery...or even a flaky battery.

'85 VN700
2005 VN750 for parts
one2 is offline  
post #3 of 6 (permalink) Old 07-31-2009, 08:24 AM
Newb with a Bullet!
krebsne's Avatar
Join Date: Jun 2008
Location: Omaha, NE
Posts: 589
iTrader: (0)
Sounds like a more extreme versions of what I am going through. You may have other issues but what I am working on is really getting my fuel intake system clean, clean, clean.

Is there rust in your tank? Has there ever been? Mine has been run with rusty tanks in the past and every time I think I have it cleaned the problem returns and I am told of some other area I need to clean. Most recently I let the floats run dry by running w/ the petcock on off and all my problems came back plus some. It has been surmised that I knocked more crud out of crannies by doing this, maybe even the fuel lines themselves.

So this weekend I am taking off and cleaning the carbs again. Bought actual carb dip this time. Going to drain and rinse the tank thoroughly and get completely new gas. Rebuild and clean petcock. Replace all fuel and vacuum lines. Install inline fuel filters.

Your situation does sound like it could have an electrical component as well, but IMO those are harder to diagnose. I would make sure your fuel intake is clean as a whistle and then see what it does. If nothing else you eliminate that from the equation and the symptoms might be more diagnosable.

As far as that goes, going from my experience on other bikes, what you're describing could come from a bad battery and/or CDI.

Current VN: 03 VN1600A

Past VNs: 92 VN750A, 98 VN1500A

Future VN: 94/97 VN1500A basketcase/bobber
krebsne is offline  
post #4 of 6 (permalink) Old 07-31-2009, 09:15 AM
Join Date: Apr 2009
Posts: 96
iTrader: (1)
This is what I would do....first to find out what system is causing the problem (fuel, electrical) remove the gas tank and pour the gas into a container, to see if you have rust and gunk in the gas, if so this is the first system to suspect.Clean the tank, including the petcock. You may even have to go into the carbs. If your fuel is clean then test your electrical system, with the bike running, hook a volt meter set to 50volts DC to your battery, rev the engin to around 4000rpm, you should see the needle move or if digital see it go from 12volts to around 14volts. Try this and let us know how it checks out and we can try to help you further.I guess I should have read a little further to see what you have already done. Looks like you have been working on the fuel side of things, now check the electrical, a bad battery or charging system can cause some of the things you are seeing.

Last edited by CapHAB; 07-31-2009 at 09:21 AM.
CapHAB is offline  
post #5 of 6 (permalink) Old 07-31-2009, 06:52 PM
Members who have donated towards server costs
fergy's Avatar
Join Date: Mar 2006
Location: Kyle, Texas
Posts: 4,054
iTrader: (3)
Good suggestions above. Check all your grounds and connections. Pull your plugs and check condition. Are they wet, black, brown, white??? It really sounds like carb and fuel delivery, but sometimes other things can send you in the wrong direction. You gotta look for clues and then try to focus on what might be going on. Keep up the chatter about what you are doing and finding and there will be support for you here! Good luck!

Kyle, TX VN750.com member #707 VROC#19556
2002 VN1500 Classic
Spline Lube Procedure, with photos, R/R Relocation and Coil Mod
Rusty Tank Cleaning!
Electrical Fault Finding Flowchart

fergy is offline  
post #6 of 6 (permalink) Old 07-31-2009, 07:11 PM
Calif Rider
weh44att's Avatar
Join Date: Jan 2006
Location: Petaluma Calif
Posts: 725
iTrader: (0)
Can you take a compression test of the cylinders? How old is the bike or how many miles on the speedo. I had a car once that had a chipped valve seat and it would not idle at all unless you kept it at a high RPM. Just something else to look at, may not be of help. Hope you find the trouble soon, before you really do get discouraged.

2004 25,500 miles
Led tail light enhancement
Homemade floor boards
Headlight modulator
Extra heat sink on R+R
R+R relocation
Homemade driver's backrest
Fused Stator
Mcct conversion-cost 4.50
Ride-on in tires
crash bar with home made hyway pegs
iridium plugs
home made fork wind deflectors
coil pickups adjusted.
Kenda kruz tires 110/90 170/80
weh44att is offline  
Sponsored Links


Quick Reply

Register Now

In order to be able to post messages on the Kawasaki Vulcan 750 Forum : Kawasaki VN750 Forums forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.

Once registered, your User Name"cannot be changed". We can make exceptions within 7 days, but after that, it is set in stone.

User Name:
Please enter a password for your user account. Note that passwords are case-sensitive.


Confirm Password:
Email Address
Please enter a valid email address for yourself.

Email Address:


Thread Tools
Show Printable Version Show Printable Version
Email this Page Email this Page
Display Modes
Linear Mode Linear Mode

Posting Rules  
You may post new threads
You may post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On

For the best viewing experience please update your browser to Google Chrome