Backfiring etc - Kawasaki KLR 650 Forum
1987 to 2007 Wrenching & Mods For maintaining, repair or modifications of Generation 1 KLR's. 2007 and earlier.

Reply
 
LinkBack Thread Tools Display Modes
post #1 of 11 Old 05-22-2012, 03:49 PM Thread Starter
Neutral
 
Join Date: Apr 2012
Location: Southeast or on an airplane going somewhere else.
Posts: 4
Backfiring etc

Hello all - I'm new to the group and have enjoyed the wealth of info here on the forum. Just picked up a well used '98 KLR650. Came with a Two Bros pipe, which I just repacked to a quieter db level. No idea what else has been done besides the doohickey mod, save for a non-vacuum petcock. The vacuum barb on the carb is capped. Here's my issue, and I have read (I think) all of the comments on backfiring in the forum. It only backfires on decel, seems to get worse when fully warmed up. It doesn't sound as bad as some have described their backfire issues, but it scares motorists and pedestrians in some neighborhoods. I can't find any vacuum leaks or exhaust leaks at the head or anywhere in the pipe, and it shows no sign of running lean under acceleration so it likely has the proper jet and/or the 22 cent mod already in place. Before I tear into the carb, is it common for the air cut off diaphragm to go bad? That seems to be the next stop. Looks like I can check that without taking it off the bike. I'd appreciate any advice in this area before I go any further.
pickindoug is offline  
Sponsored Links
Advertisement
 
post #2 of 11 Old 05-22-2012, 04:19 PM
Banned
 
Join Date: Jan 2010
Location: Mid-Atlantic
Posts: 763
Adjust fuel screw (my suggestion), about 1.75 turns out after soft bottoming.

Air cut valve, coasting enricher, anti-backfire valve seldom goes bad; a little backfiring upon deceleration ain't no thang, IMHO.
LoneRider is offline  
post #3 of 11 Old 05-22-2012, 05:31 PM
Missed Gear
 
Cabrito's Avatar
 
Join Date: Feb 2011
Location: 415&707
Posts: 1,193
Quote:
Originally Posted by LoneRider View Post
Adjust fuel screw (my suggestion), about 1.75 turns out after soft bottoming.

Air cut valve, coasting enricher, anti-backfire valve seldom goes bad; a little backfiring upon deceleration ain't no thang, IMHO.
This x 2.
Adjusting the air / fuel screw on the bottom of the Carb took care of 90% of my popping on decell. I installed a thumb screw trpe on mine to make it easy to adjust.

Sent from my rotary phone
================================
Track me here -
https://spotwalla.com/tripViewer.php...354a61e5f3997a
Michael G in SF | 2018 KTM 1090R Adventure | 02 XR400R (Plated) | 2011 FJ Cruiser Army Green |
------------------------------------------------------------
"If you have the will and not the way, you wont get very far."
Snakeboy66
Cabrito is offline  
 
post #4 of 11 Old 05-22-2012, 08:41 PM Thread Starter
Neutral
 
Join Date: Apr 2012
Location: Southeast or on an airplane going somewhere else.
Posts: 4
Many thanks

Lone Rider & Cabrito - thanks for the advice. Will give it a try tomorrow.

Wanted to give you guys some feedback, and thanks again for the advice. Rather than tilt the carb to do the prescribed 1.75 turns, I made a little knurled handled screwdriver that allowed me to adjust in small increments - turning it about 1/8 turn, just a little more than a bump made a 50% difference. Then I noticed the carbon tracking around the coupling where the Two Bro pipe tube attaches to the stock header pipe. Didn't notice it before but I may be running the bike a bit harder than the prior owner. Have a feeling that once I seal that up, whatever backfiring occurs will be minimal. I will say that this bike starts faster than any carbureted bike I've ever owned. Seems like it's running the second I hit the starter.

Last edited by pickindoug; 05-27-2012 at 08:53 PM.
pickindoug is offline  
post #5 of 11 Old 05-22-2012, 10:01 PM
2nd Gear
 
terry_1956's Avatar
 
Join Date: Aug 2010
Location: Casper, WY
Posts: 389
+1 on the idle mixture screw, have a friend that put on an aftermarket pipe and didn't get a good seal between it and headpipe causing backfires. You can momentarily block exhaust at pipe to check seal at headpipe joint.
terry_1956 is offline  
post #6 of 11 Old 05-23-2012, 05:17 AM
1st Gear
 
MJohnson650's Avatar
 
Join Date: Dec 2011
Location: Eugene, Or
Posts: 40
I too agree with the previous posters, check your idle mixture screw. If that dosn't work, I would next pull your header and check and replace the exhaust manifold gasket. If the PO pulled the headpipe and didn't replace the gasket with a new one there is potential that it didn't seat properly and there is an exhaust leak at the head. There is a exhaust manifold gasket seating procedure that should be followed, just FYI.
MJohnson650 is offline  
post #7 of 11 Old 05-27-2012, 01:14 AM
2nd Gear
 
Join Date: Nov 2011
Location: western north carolina
Posts: 184
hello
mines about the same,, but really when heavy in/out of throttle.. it will crackle,pop, and shoot a flame out the back,,you can see at night!!! think is funny when does backfire an people duck/jump/look in ahh ,,what th..lol..!!!!

do have stage three jet kit, full exhaust, almost positive .22cent mod not done!?
yes, notice if pipe not fully sealed agianst engine it will back fire more, an is just louder.... but after new gasket/sealant it will still back fire, when heavy/fast in/out of throttle....

so is it comman for the klr to have a deceleration popping/back-fireing issue???
can this hurt the bike if not fixed??
wnc/mtn=klr is offline  
post #8 of 11 Old 05-27-2012, 01:23 AM
OverDrive
 
Join Date: Jan 2011
Location: NW MO
Posts: 5,451
I don't know if it's common, but I did the .22 Mod and the Low-Buck Exhaust Mod only and my mild factory backfiring is non-existent. Doesn't matter if it's mild or heavy deceleration, it never pops at all. It never bothered me in the first place, but there's no doubt these 2 mods cured the problem.

It's now the only Thumper I've ever owned that doesn't pop. I would say that, for some reason, I got the idle mixture screw just right.




Last edited by planalp; 05-27-2012 at 01:32 AM.
planalp is offline  
post #9 of 11 Old 05-27-2012, 01:35 AM
2nd Gear
 
Join Date: Nov 2011
Location: western north carolina
Posts: 184
aftermarket ?

Quote:
Originally Posted by planalp View Post
I don't know if it's common, but I did the .22 Mod and the Low-Buck Exhaust Mod only and my mild factory backfiring is non-existent. Doesn't matter if it's mild or heavy deceleration, it never pops at all. It never bothered me in the first place, but there's no doubt these 2 mods cured the problem.

It's now the only Thumper I've ever owned that doesn't pop.
ya my other one only has fmf mid-pipe with stock-mod-ed muffler with stock jet..it never has back fired (maybe pa,pa,pa) nothing like my tuned moto-ed klr...

so maybe is just exhaust =aftermarket has more back pressure!!??
wnc/mtn=klr is offline  
post #10 of 11 Old 05-27-2012, 02:33 AM
Banned
 
Join Date: Jan 2010
Location: Mid-Atlantic
Posts: 763
Quote:
Originally Posted by wnc/mtn=klr View Post
so is it comman for the klr to have a deceleration popping/back-fireing issue???
can this hurt the bike if not fixed??
1. No

2. Yes, although backfiring is only the symptom of incorrect air/fuel mixture; the incorrect mixture would be the proximate cause of any damage (e.g., burned valve, etc.).

The KLR has a device, called air cut valve/coasting enricher/anti-backfire valve; possibly defective on your bike; also suspect, exhaust or intake plumbing leak, improper jetting.

Backfiring may be harmless, and some may enjoy the additional attention the additional noise provides, as with a loud exhaust.
LoneRider is offline  
Sponsored Links
Advertisement
 
Reply

Quick Reply
Message:
Options

Register Now



In order to be able to post messages on the Kawasaki KLR 650 Forum forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.

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



Similar Threads
Thread Thread Starter Forum Replies Last Post
Serious backfiring issue messenger1 2008+ KLR650 Wrenching & Mod Questions 5 05-13-2012 09:54 PM
Sudden Backfiring on an 08??? SteveB 2008+ KLR650 Wrenching & Mod Questions 1 08-02-2009 02:03 AM
09 Backfiring kpacman 2008+ KLR650 Wrenching & Mod Questions 8 05-24-2009 09:48 PM
Air in fuel line and backfiring help needed. rideaholic 1987 to 2007 Wrenching & Mods 8 03-23-2009 10:25 PM
Bike dying and backfiring??? joker 1987 to 2007 Wrenching & Mods 24 09-08-2008 08:46 AM

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