Go Back  Offshoreonly.com > Technical > General Q & A
Carb backfire (lean condition) theory? >

Carb backfire (lean condition) theory?

Notices

Carb backfire (lean condition) theory?

Old 07-11-2004, 06:47 PM
  #1  
Registered
Thread Starter
 
Join Date: Nov 2003
Posts: 371
Likes: 0
Received 1 Like on 1 Post
Default Carb backfire (lean condition) theory?

I just read that a lean condition does not burn the fuel as it should, so it kind of builds up a bit and then backfires! somehow it ignites in the intake and out through the carb it goes... wtf? in my mind I can only see fire in that direction if the intake valve is open and you spark... i.e. very bad timing, or cross spark. I would think if timing was so advanced that your sparking while the intake valve is open... it would happen every stinking spark!?

My question is... how the hell does this unburnt fuel ignite in the intake??

I just had a carb backfire singe my eyebrows (i was watching the fuel from the accelerator pump, blipped the throttle a little, and POW!!! shotgun in the face!) sounds funny, but I've been battling this problem far too long... it's on the verge of kicking my ass! j/k... never happen! I've read every stinking post here on OSO, and everywhere else on the internet carb backfire was found....... in 4 languages!! Mita vittu, perkele satana helvitti!!!
jackhammer is offline  
Old 07-12-2004, 03:23 PM
  #2  
Registered
 
aero-offshore's Avatar
 
Join Date: Apr 2001
Location: muskegon, michigan
Posts: 586
Likes: 0
Received 0 Likes on 0 Posts
Default Re: Carb backfire (lean condition) theory?

I know it does the same thing on a Harley if the carb is lean, pops out the carb, somene said it was because the previous combustion charge could not completely burn from lack of oxygen and when you open the throttle it corrects the needed oxygen for the still trying to burn charge and POP it burns thru the intake runner.
aero-offshore is offline  
Old 07-12-2004, 03:38 PM
  #3  
Charter Member
Charter Member
iTrader: (1)
 
Ted G's Avatar
 
Join Date: Jan 2001
Location: Edgerock Baby!!
Posts: 7,663
Likes: 0
Received 1 Like on 1 Post
Default Re: Carb backfire (lean condition) theory?

In some cases the lean mixture will cause the cylinder temp go up, and then either the hot spark plug or the exhaust valve ignites the mixture as it enters the cylinder(before the intake valve closes)-thus you get a pop.
__________________
Chesapeake Bay Powerboat Association
www.cbpba.com
Ted G is offline  
Old 07-13-2004, 01:05 PM
  #4  
Registered
 
Join Date: Oct 2002
Location: nowhere
Posts: 263
Received 11 Likes on 6 Posts
Default Re: Carb backfire (lean condition) theory?

Rule of thumb is,
Popping in the carb........lean mixture.
Popping out the exhaust is .....yep.......rich mixture.
OPIE272 is offline  
Old 07-13-2004, 08:01 PM
  #5  
Registered
Thread Starter
 
Join Date: Nov 2003
Posts: 371
Likes: 0
Received 1 Like on 1 Post
Default Re: Carb backfire (lean condition) theory?

The carb shop is sending two sets of Power Valves, two sets of #80 Jets and two sets of #86 Jets... I don't know what they put in to start with (I'll soon find out). Hmmm... I wonder why he's not suggesting to change accelerator pumps? I have a feeling I'm going to get to know these carbs very well!!
jackhammer is offline  
Related Topics
Thread
Thread Starter
Forum
Replies
Last Post
madorno1
General Boating Discussion
1
09-22-2007 11:05 PM
GNJ
General Q & A
7
04-28-2005 10:58 AM
MitchStellin
General Q & A
17
05-17-2004 09:01 PM
BAD-HABIT
General Q & A
6
05-16-2003 08:35 AM

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


Quick Reply: Carb backfire (lean condition) theory?


Contact Us - Archive - Advertising - Cookie Policy - Privacy Statement - Terms of Service

Copyright © 2024 MH Sub I, LLC dba Internet Brands. All rights reserved. Use of this site indicates your consent to the Terms of Use.