VT1100 Backfire - Honda Shadow Forums : Shadow Motorcycle Forum

Reply
 
LinkBack Thread Tools
Old 12-08-2009, 09:42 PM   #1 (permalink)
Junior Member
 
cignadude's Avatar
 
Join Date: Nov 2009
Posts: 25
Default VT1100 Backfire

Hi guys, me again. I've been tinkering with the bike and found that the air/fuel mixture screw on the right hand (brake side) of the bike doesn't affect the running of the bike at all. If I screw the one on the left side (clutch side) the bike will die but with it idling I can screw the right side screw all the way in or out and it does nothing. The bike still backfires on deceleration and now it does the same on acceleration. I have sync'd the carbs and tried setting mixture screws at 3.25 turns each (i have aftermarket Vance & Hines exhaust) Even when the right side screw is all the way in it appears the front cylinder still fires after you turn the throttle a little way. it doesn't appear to be firing at idle.
__________________
94 VT1100
cignadude is offline   Reply With Quote
Sponsored Links
Advertisement
 
Old 12-08-2009, 11:58 PM   #2 (permalink)
Senior Member
 
dwmitchell61's Avatar
 
Join Date: Aug 2007
Location: Kennewick, WA
Posts: 2,935
Send a message via MSN to dwmitchell61 Send a message via Yahoo to dwmitchell61
Default

Maybe teh carburetor synch is way out, throttles not opening simultaneously?
__________________
David W. Mitchell
Patriot Guard #145143
Standing for those who stood for us.
American Legion Rider Kenn-Pasco Chapter 34

1999 Honda Valkyrie F6 GL1500C
dwmitchell61 is offline   Reply With Quote
Old 12-09-2009, 01:17 AM   #3 (permalink)
Senior Member
 
Join Date: May 2007
Location: LEAVENWORTH WASHINGTON
Posts: 5,286
Default

How did you sync the carbs, sounds like there not, very typical condition when there not and it doesn't take all that much,,in fact it takes very little to get that reaction.
__________________
Ted
SHADOW 1100T is offline   Reply With Quote
Old 12-09-2009, 11:32 AM   #4 (permalink)
Senior Member
 
Join Date: Apr 2008
Location: Palatine, IL
Posts: 6,561
Default backfire

It sounds like the idle mixture needle on the right side might be damaged or the seat on the side might be damaged. With the bike off unscrew the one on the right all the way out and inspect it for damage. The other possiblity is that it might not be a problem with the idle mixture, it could be a problem with the mid or high section of the carb the is allowing gas to enter the carb at idle.
jpr1968 is offline   Reply With Quote
Old 12-09-2009, 05:11 PM   #5 (permalink)
Junior Member
 
cignadude's Avatar
 
Join Date: Nov 2009
Posts: 25
Default

I sync'd with vacuum gauges but I couldn't guarantee it's still on the money. I will re-sync and see if it helps.

If its a seat or other carb problem would it still be firing at higher rpm's?
__________________
94 VT1100
cignadude is offline   Reply With Quote
Old 12-09-2009, 07:36 PM   #6 (permalink)
Senior Member
 
Join Date: May 2007
Location: LEAVENWORTH WASHINGTON
Posts: 5,286
Default

One of the problems with Vac gages is that they can get out of adjustment, they need to be hooked to a common manifold with a given amount of vacuum (needle in the center of the gage) applied to be sure they both read the same, there's a adj screw on the back to adj it with.
__________________
Ted
SHADOW 1100T is offline   Reply With Quote
Old 12-12-2009, 03:59 PM   #7 (permalink)
Junior Member
 
cignadude's Avatar
 
Join Date: Nov 2009
Posts: 25
Default

double checked carb sync and I even cross checked the gauges to make sure they both read the same. adjusted it a little but they were spot on afterwards with no change. When you put your hand over the exhaust pipe for the front cylinder you feel cold air. Does that mean fuel or spark? I switched the coils and the bottom cylinder acted like it wanted to fire with the choke on but at normal idle still nothing. Should I continue chasing spark issue's? could it be an ignitor and if so where are they located and can they be checked? Or are we still looking at carb problem?
__________________
94 VT1100
cignadude is offline   Reply With Quote
Old 12-12-2009, 04:31 PM   #8 (permalink)
Senior Member
 
Join Date: May 2007
Location: LEAVENWORTH WASHINGTON
Posts: 5,286
Default

Is it running on 1 cylinder? if it is then when you switched the coils it would mean the coil is good and it's a fuel problem, did yo check the diaphragms on the slides?, if there's even a tiny hole/crack it won't want to lift like it should.
__________________
Ted
SHADOW 1100T is offline   Reply With Quote
Old 12-12-2009, 06:04 PM   #9 (permalink)
Junior Member
 
cignadude's Avatar
 
Join Date: Nov 2009
Posts: 25
Default

it is running on 1 cylinder. I have confirmed that full choke makes the front cylinder try to fire which tells me it's starving for gas. The bike did sit up for awhile prior to me buying it so the carb is probably dirty. Tomorrow I'm going to put it back together and take it for a long ride with some MMO and B-12 in the tank and see if it will work it helps. If not, its time to take the carbs off for a good cleaning. I'm a little nervous about doing that which is why I'm trying everything else first.
__________________
94 VT1100
cignadude is offline   Reply With Quote
Old 12-12-2009, 06:06 PM   #10 (permalink)
Junior Member
 
cignadude's Avatar
 
Join Date: Nov 2009
Posts: 25
Default

are the slide diaphragms accessible without taking the carb off the bike?
__________________
94 VT1100
cignadude is offline   Reply With Quote
Sponsored Links
Advertisement
 
Reply

Thread Tools

Posting Rules
You may not post new threads
You may not 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



All times are GMT -4. The time now is 03:19 AM.



Powered by vBulletin® Copyright ©2000 - 2014, Jelsoft Enterprises Ltd.
Search Engine Optimization by vBSEO 3.6.0
Garage Plus vBulletin Plugins by Drive Thru Online, Inc.
Motorcycle News, Videos and Reviews
Honda Grom Forum Harley Davidson Forum Honda 600RR Kawasaki Forum Yamaha R6 Forum Yamaha FZ-09 Forum
1199 Panigale Forum Roadglide Forum Honda CBR1000 Forum Vulcan Forum Yamaha R1 Forum Yamaha R3 Forum
Ducati Monster Forum Harley Forums Honda CBR250R Forum ZX10R Forum Star Raider Forum Yamaha Viking Forum
Suzuki GSXR Forum V-Rod Forums Honda Shadow Forum Kawasaki Motorcycle Forum Star Warrior Forum KTM Duke 390 Forum
SV650 Forum BMW S1000RR Forum Honda Fury Forum Kawasaki Versys Forum Drag Racing Forum Ducati 899 Panigale Forum
Suzuki V-Strom BMW K1600 Triumph Forum Victory Forums Sportbikes BMW NineT Forum
Volusia Forum BMW F800 Forum Triumph 675 Forum MV Agusta Forum HD Street Forum Suzuki GW250 Forum
Yamaha Motorcycles Victory Gunner Forum Honda Vultus Forum HD LiveWire Forum