ADVrider

Go Back   ADVrider > Bikes > Orange Crush
User Name
Password
Register Inmates Photos Site Rules Search Today's Posts Mark Forums Read

Reply
 
Thread Tools Search this Thread Display Modes
Old 10-26-2012, 09:56 AM   #1
5 speed OP
Studly Adventurer
 
Joined: Sep 2006
Location: Orlando Florida
Oddometer: 848
Off throttle backfire

Hi there. So It took my bike in for a valve adjustment. Generally do everything myself but havent adjusted the valves and figured I would have it done professionally. The bike was at the shop for 4 weeks as I had springs ordered for the front end and also sent my seat out to be redone. I figured the gas may have gone bad but I did have the Marine Stabilizer in it. I sprayed seafoam in the carbs and also ran some through the gas and then rode it about 500 miles. My conclusion because, it idles fine and performs well is that there is an airleak. It backfiring and spitting when the throttle is chopped. I remember putting the carbs in myself once and thought they seated but then took the tanks off and could see through the access panels that they weren't quite right.

So, before I pull the tanks, any ideas of how I might tell where the airleak is coming from (with suspect that it may have to do with the dis/reassembly from the valve job). your thoughts would be appreciated.
5 speed is offline   Reply With Quote
Old 10-26-2012, 11:01 AM   #2
snowhawk jockey
Slack Jaw Gaper
 
snowhawk jockey's Avatar
 
Joined: Jul 2005
Location: The other Center of the Universe: Bend, Oregon
Oddometer: 1,086
Did the shop fiddle with your exhaust at all? Air leak there is a sure backfire.
snowhawk jockey is offline   Reply With Quote
Old 10-26-2012, 12:30 PM   #3
TheMuffinMan
Forest Ranger Magnet
 
TheMuffinMan's Avatar
 
Joined: Mar 2010
Location: Denver, USA
Oddometer: 5,116
I'd make sure the carbs are seated in the boots, and then I'd be going over the exhausts for cracks/leaks.
__________________
"All that is gold does not glitter,
Not all those who wander are lost;
The old that is strong does not wither,
Deep roots are not reached by the frost."
'12 690 Enduro // 690 Wiki
TheMuffinMan is offline   Reply With Quote
Old 10-26-2012, 01:08 PM   #4
Spiritwalker2222
Gnarly Adventurer
 
Joined: Sep 2010
Location: Ottawa, Canada
Oddometer: 112
Check you exhaust header. If the bolt and nut are loose it can cause your bike to bikefire whenever you let off the throttle.
Spiritwalker2222 is offline   Reply With Quote
Old 10-26-2012, 02:45 PM   #5
5 speed OP
Studly Adventurer
 
Joined: Sep 2006
Location: Orlando Florida
Oddometer: 848
Cool I will try those suggestions before I jump on the carbs and report back. Thanks much
5 speed is offline   Reply With Quote
Old 10-27-2012, 04:38 AM   #6
DirtyADV
Beastly Adventurer
 
DirtyADV's Avatar
 
Joined: Jan 2007
Location: SWEDEN, Skellefteå
Oddometer: 1,920
Had bad backfiring when engine braking from like 4500 rpm and below.

Carbs were not touched when the bike developed this, found it to be an air leak on one of the hoses on the intake below the carbs that are used when syncing the carbs (smog stuff removed).

Poorly seated or torn intake rubber could probably cause it also.

/Johan
__________________
Have changed name, was previously Dirty950

www.dirtyadv.com (under construction)
DirtyADV is offline   Reply With Quote
Old 10-27-2012, 08:05 PM   #7
5 speed OP
Studly Adventurer
 
Joined: Sep 2006
Location: Orlando Florida
Oddometer: 848
I guess I got ahead of myself. I fired it up in the driveway and it ran and idled fine, no backfiring. So I put it together last night (had not gone so far as pulling the tanks) and today it ran terrific, idled perfect, but still backfires when winding down from about 4,000 RPM. It seems to be the right pipe which is the front cylinder. I checked around the head and the pipe joint and did not find a leak. as far as the carbs i did as much inspection from topside I could and the carbs seem seated (although I have been fooled before on that one). I would say its definitely an airleak.
5 speed is offline   Reply With Quote
Old 10-27-2012, 11:12 PM   #8
MrEndo
Gnarly Adventurer
 
MrEndo's Avatar
 
Joined: May 2006
Location: Sacramento, CA
Oddometer: 415
U can spray a carb cleaner like Berryman B12 on the areas you suspect are leaking. If the idle goes up or down it is sucking the spray in through a leak. Be cautios not to spray so much that it is getting sucked in the carb intake. You might need to hold it at a fast idle for best results.
__________________
2014 Harley Ultra Limited
2013 350 EXC-F (Wife's)
2008 530 EXC-R/2008 Beta Rev4T
2006 950 Adv S/2002 640 Adv/1970 Yamaha RT1
MrEndo is offline   Reply With Quote
Old 10-27-2012, 11:18 PM   #9
geometrician
let's keep going...
 
geometrician's Avatar
 
Joined: May 2008
Location: West-By-God Virginia
Oddometer: 1,023
Intake not exhaust leak

Quote:
Originally Posted by MrEndo View Post
U can spray a carb cleaner like Berryman B12 on the areas you suspect are leaking. If the idle goes up or down it is sucking the spray in through a leak.
WD40 works just as well & isn't caustic as carb cleaners are

air leak WAY more likely to be the cause than exhaust
__________________
Britt
'06 KTM 950 Adv 'S'
'03 KTM 250 EXC
'87 KLR650 - <200K miles "Like the Energizer Bunny, just keeps going & going..."
geometrician is online now   Reply With Quote
Old 10-27-2012, 11:31 PM   #10
MrEndo
Gnarly Adventurer
 
MrEndo's Avatar
 
Joined: May 2006
Location: Sacramento, CA
Oddometer: 415
Quote:
Originally Posted by geometrician View Post
WD40 works just as well & isn't caustic as carb cleaners are

air leak WAY more likely to be the cause than exhaust
I was suggesting it for an intake leak....
__________________
2014 Harley Ultra Limited
2013 350 EXC-F (Wife's)
2008 530 EXC-R/2008 Beta Rev4T
2006 950 Adv S/2002 640 Adv/1970 Yamaha RT1
MrEndo is offline   Reply With Quote
Old 10-28-2012, 05:53 AM   #11
5 speed OP
Studly Adventurer
 
Joined: Sep 2006
Location: Orlando Florida
Oddometer: 848
Yes I will try that and see. I do have a question however, I have noticed that when looking at the slides in the carbs, when pulling the throttle cable one opens slightly sooner than the other, I think the rear carb is opening first. Is that correct?
5 speed is offline   Reply With Quote
Old 10-28-2012, 07:13 AM   #12
StmbtDave
AKA Invisible Dave
 
StmbtDave's Avatar
 
Joined: Aug 2005
Location: Loveland, CO summer - Green Valley, AZ winter
Oddometer: 2,851
Quote:
Originally Posted by 5 speed View Post
Yes I will try that and see. I do have a question however, I have noticed that when looking at the slides in the carbs, when pulling the throttle cable one opens slightly sooner than the other, I think the rear carb is opening first. Is that correct?
No, that is not correct. Both should open exactly at the same time and open the exact same amount. What you're seeing may be caused by one of the throttle cables not being seated correctly or as it was in my case, one of the carb diaphrams being torn. I would first check the cables as they may have been disturbed during the shop work.

Dave
__________________
Why are we stopping? We don't have time for that!
StmbtDave is offline   Reply With Quote
Old 10-28-2012, 07:34 AM   #13
Boatman
Ride more, BS less!
 
Boatman's Avatar
 
Joined: Mar 2005
Location: Petersburg, NY and Woodbridge, VA
Oddometer: 9,924
Slides are vacuum controlled... butterflies are operated by the cables. All should work identical (for the most part) between carbs. If one of the slides are lagging, it could be hanging up or a vacuum leak or a pin hole in a diaphram or some other small issue could cause that.

Also carb sync could be at the root of the problem.
__________________
08 KTM 950 SE, 09 KTM 950 SE, 04 KTM 950 ADV, 10 Husaberg FE390, 66 Kawasaki B8S Super 150

Hi/low beam conversions for: Trail Tech, Baja Designs
Boatman is offline   Reply With Quote
Old 10-28-2012, 08:29 AM   #14
geometrician
let's keep going...
 
geometrician's Avatar
 
Joined: May 2008
Location: West-By-God Virginia
Oddometer: 1,023
Air Cut Valve

Quote:
Originally Posted by MrEndo View Post
I was suggesting it for an intake leak....
that's what we're talking about... not trying to set the bike on fire!

on the many bikes that use this CVK carb the air-cut valve diaphragm is the known culprit for backfiring on closed throttle

it's item #34 on the carb parts diagram...
__________________
Britt
'06 KTM 950 Adv 'S'
'03 KTM 250 EXC
'87 KLR650 - <200K miles "Like the Energizer Bunny, just keeps going & going..."
geometrician is online now   Reply With Quote
Old 10-28-2012, 08:45 PM   #15
K2m
....58....
 
K2m's Avatar
 
Joined: Feb 2005
Location: Sydney Australia
Oddometer: 2,242
Quote:
Originally Posted by 5 speed View Post
I guess I got ahead of myself. I fired it up in the driveway and it ran and idled fine, no backfiring. So I put it together last night (had not gone so far as pulling the tanks) and today it ran terrific, idled perfect, but still backfires when winding down from about 4,000 RPM. .
When a LC8 is perfectly tuned they do this.

It may be possible to tune it out by changing the Air Leak jet on the ACV (air cut valve) it's on the pilot circuit.

If you wish to explore this option I can help further.

If I understand correctly :-
It came back from the shop popping on decel. ..... Spot on.
__________________
The News, those who are trying to control what we think, do not want us to see.
http://www.presstv.ir/live.html So good the British Gov. Banned it !!!
http://rt.com/on-air/rt-america-air/
K2m is offline   Reply With Quote
Reply

Share

Thread Tools Search this Thread
Search this Thread:

.
Display Modes

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 On

Forum Jump


Times are GMT -7.   It's 01:37 AM.


Powered by vBulletin® Version 3.8.5
Copyright ©2000 - 2014, Jelsoft Enterprises Ltd.
Copyright ADVrider 2011-2014