Front Cylinder popping on decel... - Kawasaki Vulcan 750 Forum : Kawasaki VN750 Forums
Carbs and Fuel System
From the gas tank to the carbs
All fuel system discussion

Reply
 
LinkBack Thread Tools Display Modes
post #1 of 15 (permalink) Old 06-25-2009, 03:01 AM Thread Starter
1992 VN 750
 
bordolover's Avatar
 
Join Date: Jan 2009
Location: Colorado Springs, CO
Posts: 109
iTrader: (1)
 
Front Cylinder popping on decel...

I have not been able to reduce the popping from the front cylinder even after coastering and then setting the air/fuel mixture screws to 2 3/4 turns out. The rear cyclinder is just about right...no popping on decel at all at about 2 1/2 turns out. How far out is it "safe" to turn the air/fuel mixture screw out before I risk it coming out altogether or negate its purpose in the first place?

Is it normal for one cyclinder to be this different from the other? I have V and H Cruzers...would it make sense to put a larger slow speed jet on the front carb or would this not provide the desired effect? I need to find a way to stop the popping/backfiring pretty soon...with the Cruzers and having to slow down quickly from 70 to 30 to go through these quaint little German towns the tranquility of these peaceful mornings are being shattered by the ever-present Kawasaki Vulcan pop/backfires!

KM...I enjoyed the reply on the purpose of the right ear hose and its associated effect on carb performance! Good stuff...

1992 VN 750 / 18,100 miles
V and H Cruzers
Earshaved and sheared
110/90 and 170/80 Metzeler 880s
AGM Battery
TPE Stator
Clear Alternatives LED brakelight
Saddleman Explorer Seat
Kurakyn Levers
VN750.com Grill cover
SCP Coasters
Iridium plugs
MOSFET R/R
bordolover is offline  
Sponsored Links
Advertisement
 
post #2 of 15 (permalink) Old 06-25-2009, 06:28 AM
Members who have donated towards server costs
 
750Doug's Avatar
 
Join Date: Apr 2008
Location: S.E. Michigan
Posts: 2,850
iTrader: (10)
   
You could probably safely turn it out some more, maybe up to a whole turn. Try it a quarter turn at a time and see.

Or, screw it all the way in, and then count the turns out til it falls out, reinstall, and take it from there.

In the year and a half I've been hanging around here, I've seen a variety of numbers mentioned as to how many turns is safe until it will fall out....
750Doug is offline  
post #3 of 15 (permalink) Old 06-25-2009, 06:29 AM
The Professor
 
lance328's Avatar
 
Join Date: Feb 2008
Location: BUFORD, GEORGIA
Posts: 3,147
iTrader: (15)
   
The popping is caused by an exhaust leak or excess fuel igniting when it hits the hot exhaust.

It is normal for one cylinder to be different, normaly you would run the front cylinder leaner than the rear.

Turn the pilot screw in and lean the pilot air/fuel mixture on the front cylinder. If that does not help you may have an exhaust leak.


85 VN700 "Old Yella"

REBUILT ENGINE
CUSTOM PAINT
VANCE & HINES CRUZERS
EAR SHAVED AND RE-JETTED W/K&N'S
DUNLOP ELITE K591 FRONT & REAR
VOLTMETER
SYNTHETIC BRAKE FLUID
SYNTHETIC OIL & GEAR LUBE
PLEXISTAR 2 WINDSHIELD
SPLINES LUBED
ACCT'S GREASED W/TOC SPRINGS
COASTERD
LEATHER SADDLE BAGS
LEATHER TOOL AND ROLL BAG
PICKUP COILS GAPPED AT .018"
NGK CAP, WIRES, IRIDUMS
BARNETT FRICTION PLATES & SPRINGS
CUSTOM GRIPS, MIRRORS, LEVERS
ORIGINAL STATOR & R/R 14.5v
DEKA MF AGM ETX15L

Best Auto/Moto Insurance | Motorcycle Protection Today | FREE Trade-In Quote
lance328 is offline  
 
post #4 of 15 (permalink) Old 06-25-2009, 11:26 AM Thread Starter
1992 VN 750
 
bordolover's Avatar
 
Join Date: Jan 2009
Location: Colorado Springs, CO
Posts: 109
iTrader: (1)
 
OK...I will look at the exhaust and see if there might be a leak. I used new gaskets but perhaps they are not torqued properly or theymight be binding somewhere and not able to seat correctly. The V and H pipes snug up pretty well so I will look at the left side again and see if I can find something or see if the HD gaskets will work better. The ones I bought from Kawasaki seemed a bit on the "lean" side anyway! Ha.

SO..pipes loosened, reset, and retorqued and see if that makes any difference in the popping during decel. MTF...

1992 VN 750 / 18,100 miles
V and H Cruzers
Earshaved and sheared
110/90 and 170/80 Metzeler 880s
AGM Battery
TPE Stator
Clear Alternatives LED brakelight
Saddleman Explorer Seat
Kurakyn Levers
VN750.com Grill cover
SCP Coasters
Iridium plugs
MOSFET R/R
bordolover is offline  
post #5 of 15 (permalink) Old 06-25-2009, 12:08 PM
Members who have donated towards server costs
 
fergy's Avatar
 
Join Date: Mar 2006
Location: Kyle, Texas
Posts: 4,054
iTrader: (3)
   
The front cyl exhaust is on the right. You can try the smoking cigarette trick to see if you have exhaust leaks.

Fergy
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
SEAFOAM JUNKIE!


fergy is offline  
post #6 of 15 (permalink) Old 06-25-2009, 12:14 PM Thread Starter
1992 VN 750
 
bordolover's Avatar
 
Join Date: Jan 2009
Location: Colorado Springs, CO
Posts: 109
iTrader: (1)
 
I know...

I used the cigar trick after I installed the V and H pipes last week but found no leak. The popping is still there but after a week and several hundred miles I can always do it again and perhaps cigarette smoke will work better...at least until the Government changes the blend and prevents any of those chemicals being added that make it taste just oh so good! Ha.

But I will readjust them and see if I can loacte a leak. They sound so good on acceleration I find it hard to believe that there is a leak...but I will continue to attack this methodically. Before I change out jets or turn the screw out 4 turns or so! It think 5 1/4 is about the limit but at 3.5 I figured it would have been cured. Maybe time to go back to the basics on this one and take them off and use another gasket. Thanks Fergy!

1992 VN 750 / 18,100 miles
V and H Cruzers
Earshaved and sheared
110/90 and 170/80 Metzeler 880s
AGM Battery
TPE Stator
Clear Alternatives LED brakelight
Saddleman Explorer Seat
Kurakyn Levers
VN750.com Grill cover
SCP Coasters
Iridium plugs
MOSFET R/R
bordolover is offline  
post #7 of 15 (permalink) Old 06-26-2009, 07:41 AM Thread Starter
1992 VN 750
 
bordolover's Avatar
 
Join Date: Jan 2009
Location: Colorado Springs, CO
Posts: 109
iTrader: (1)
 
Update...

Loosened the right side pipe and reset it and then torqued it to specs. NO change. I think I will check the carb boots and see if they might be loose and tighten if necessary to see if that might be the issue. Then time to try the HD exhaust gaskets and if nothing improves after then I am at a real loss.

Would rejetting to 135 make any difference? Make it worse? Heck...maybe I should simply enjoy the rumbles and snaps and snarls and take her to see The Professor when I move back to the states!

1992 VN 750 / 18,100 miles
V and H Cruzers
Earshaved and sheared
110/90 and 170/80 Metzeler 880s
AGM Battery
TPE Stator
Clear Alternatives LED brakelight
Saddleman Explorer Seat
Kurakyn Levers
VN750.com Grill cover
SCP Coasters
Iridium plugs
MOSFET R/R
bordolover is offline  
post #8 of 15 (permalink) Old 06-26-2009, 02:16 PM
The Professor
 
lance328's Avatar
 
Join Date: Feb 2008
Location: BUFORD, GEORGIA
Posts: 3,147
iTrader: (15)
   
Quote:
Originally Posted by bordolover View Post
Update...

Loosened the right side pipe and reset it and then torqued it to specs. NO change. I think I will check the carb boots and see if they might be loose and tighten if necessary to see if that might be the issue. Then time to try the HD exhaust gaskets and if nothing improves after then I am at a real loss.

Would rejetting to 135 make any difference? Make it worse? Heck...maybe I should simply enjoy the rumbles and snaps and snarls and take her to see The Professor when I move back to the states!
The H-D gaskets are smaller diameter than the KAW, after trying them I went back to the KAW ones.

If adjusting the pilot screw out does not change try turning the screw in, it may be getting too much fuel.

Check your front coaster and make sure you have a good seal.


85 VN700 "Old Yella"

REBUILT ENGINE
CUSTOM PAINT
VANCE & HINES CRUZERS
EAR SHAVED AND RE-JETTED W/K&N'S
DUNLOP ELITE K591 FRONT & REAR
VOLTMETER
SYNTHETIC BRAKE FLUID
SYNTHETIC OIL & GEAR LUBE
PLEXISTAR 2 WINDSHIELD
SPLINES LUBED
ACCT'S GREASED W/TOC SPRINGS
COASTERD
LEATHER SADDLE BAGS
LEATHER TOOL AND ROLL BAG
PICKUP COILS GAPPED AT .018"
NGK CAP, WIRES, IRIDUMS
BARNETT FRICTION PLATES & SPRINGS
CUSTOM GRIPS, MIRRORS, LEVERS
ORIGINAL STATOR & R/R 14.5v
DEKA MF AGM ETX15L

Best Auto/Moto Insurance | Motorcycle Protection Today | FREE Trade-In Quote
lance328 is offline  
post #9 of 15 (permalink) Old 06-26-2009, 03:26 PM
Members who have donated towards server costs
 
fergy's Avatar
 
Join Date: Mar 2006
Location: Kyle, Texas
Posts: 4,054
iTrader: (3)
   
Good points Lance. I was thinking surely he's tried turning the screw in through the process of elimination. When you coaster (I marbled) is there a gasket that goes under it?

Fergy
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
SEAFOAM JUNKIE!


fergy is offline  
post #10 of 15 (permalink) Old 06-26-2009, 04:37 PM
Linkmeister Supreme
 
OlHossCanada's Avatar
 
Join Date: Aug 2008
Location: Lethbridge, Alberta, Canada
Posts: 7,960
iTrader: (8)
   
fergy, I pulled the factory coaster plate off the front clyinder on my bike yesterday, just to take a look under it. There was no discernable gasket on the Canadian version of the bike.

Gordon

1991 VN 750 -"Cosmic Lady" or "Bad Girl"?
Purchased May 16, 2008
Approx.19,300km (12,000 miles)

H-D windshield
Relocated R/R
MF-AGM battery
Fiamm Freeway Blaster horns
F&S luggage rack and engine guard
Kury Offset Hiway pegs
July 13, 2016, Riding on the DARKSIDE now, Classic Radial 165/80-15


TOP TEN THINGS A NEW RIDER/OWNER SHOULD DO. Click on link.
https://www.vn750.com/forum/11-vn750-general-discussion/9127-top-ten-items-you-would-suggest-new-owner-do-his-new-ride.html
OlHossCanada is offline  
Sponsored Links
Advertisement
 
Reply

Bookmarks

Quick Reply
Message:
Options

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

Password:


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

Email Address:
OR

Log-in










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