carb problems? popping and cracking on when off throttle. - 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 10-17-2011, 11:41 AM Thread Starter
Junior Member
Join Date: Jun 2011
Posts: 2
iTrader: (0)
carb problems? popping and cracking on when off throttle.

Ok I need some help or at least reassurance that what I'm having is normal. I have a 1994 750 with 06 carbs. The carbs are still all factory settings as far as air screw and syncing. I have rejetted to 142/42's .I have the ears shaved with cone filters on each Carb. I am also running jardine pipes(open). I have taken the covers off the side of the heads and replaced with some coasters. And still I get the popping and cracking while of the throttle when riding. Any and all help is appreciated.
marion37303 is offline  
Sponsored Links
post #2 of 6 (permalink) Old 10-17-2011, 12:00 PM
slimvulcanrider's Avatar
Join Date: May 2008
Posts: 8,695
iTrader: (3)
adjust the air/fuel screws... screw all =the way in.. and about 2 1/2 turns out
slimvulcanrider is offline  
post #3 of 6 (permalink) Old 10-17-2011, 02:57 PM
Crap, I WAS in 5th gear.
Join Date: Sep 2011
Location: So. Cal
Posts: 500
iTrader: (1)
Check your coasting enricheners, you shouldn't have any popping when coastered, unless you have a lean condition caused somewhere in the carb, or an air leak somewhere. Afterfiring causes higher exhaust temperature, so your headers will turn blue.
Kelly2001 is offline  
post #4 of 6 (permalink) Old 10-19-2011, 03:23 PM
Junior Member
Join Date: Jun 2011
Posts: 12
iTrader: (0)
could be that a diaphragm is broken and or cracked and needs to be replaced
scubadiver is offline  
post #5 of 6 (permalink) Old 10-21-2011, 11:30 PM
Members who have donated towards server costs
Join Date: Nov 2007
Location: Chandler, Arizona
Posts: 2,888
iTrader: (0)
Unfortunately, once you deviated from factory jetting and filters, finding a solution will be trial and error. I would definitely remove the plugs and turn the pilot screws out 2 1/2-3 turns, and remove every single part of the air injection system. since you no longer have an airbox, you won't have to plug the hole in that, but you will need to cap the unused vacuum fitting on the rear carb. You will need to cap the reed valve covers on both heads, you can get coasters for this purpose, or you can do what I did, and use the original covers, with rubber caps on them. The caps I used were from Autozone, and were designed to plug heater hose fittings on cars. They fit the bike perfectly, and cost $1.99 for 2.

I am a motorcyclist, NOT a biker.

1997 Vulcan 750, purchased about a week ago
2006 Sportster 1200 Low
2013 Royal Enfield Bullet 500, converted to carb
2001 Yamaha XT225, heavily modified
2004 Honda Rebel 250
1979 Vespa P200E
2002 Vulcan 750 parts bike
1994 Yamaha XT225 parts bike
VN750Rider/Jerry is offline  
post #6 of 6 (permalink) Old 10-22-2011, 09:14 PM
dragon159's Avatar
Join Date: Dec 2007
Location: Poynette WI
Posts: 1,050
iTrader: (3)
Just another thought ..... when you changed exhaust were new crush gaskets used? Leaks there will have the same effect.

87 vn750at least that is what the frame #'s say
"Squirrel Bike" aka Jersey

Rat bike with a good PR agent

shaved and coastered
2 into 1 exhaust
rear 170 and front 110
Relocated R/R
custom dash with voltmeter
Spitfire windscreen
Plutonium plugs
Recovered seat without "butt hammers"
More to come
Praise to the Parts Goddess Crobins for needed things

When someone tells me "Great minds think alike" all I can think is "You Pervert"
dragon159 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