Backfiring through S&S carb : V-Twin Forum: Harley Davidson Forums
» Sponsors

» Insurance
Go Back   V-Twin Forum : Harley-Davidson Motorcycle Forums > V-Twin Performance Forums > Pre-Evolution Engine Mods
New User? Register Forgot Password

Reply
 
LinkBack Thread Tools Display Modes
Old 09-22-2009, 10:09 AM   #1 (permalink)
Seasoned Rider
 
JoeShovel's Avatar
 
Join Date: Aug 2008
Location: NC
Posts: 59
JoeShovel wants to know Dino or Syn?
Backfiring through S&S carb

OK, 1966 74" shovelhead with Mallorery electronic ign, S&S super E shorty carb...

Was running fine with no problems at all and now it is backfiring through the carb very badly. Feels like one cylinder is not firing at all. This all started after I went to the gas station and put in lower octane due to them not having higher octane.

Here is what I have done so far to no avail:

I have drained out all of the bad gas from the tank and carb, put new plugs in, verified that I'm getting spark to the bad cylinder, adjusted timing...

I'm at a loss at this point. Every electronic component was replaced and rebuilt over the summer so I'm only left to think it is a mechanical issue which I hope it isn't.

Any thoughts?
__________________
1973 FX frame chopped in the rear with rigid welded in place. Bottom end is 58 panhead topped with 66 shovelhead. S&S super E carb, Andrew B grind cam. 73 4spd trans. Kick and Electric start... A bobber fo sho
JoeShovel is offline   Reply With Quote Quick reply to this message
Sponsored Links
Advertisement
 
Old 09-22-2009, 10:25 AM   #2 (permalink)
XLIII
 
MegaGlide's Avatar
 
Join Date: Sep 2004
Location: West Central Indiana
Posts: 10,079
MegaGlide wants to know Dino or Syn?
Are the plug wires new?
If not, check to see if the one going to the non-firing cylinder is rubbed through somewhere and shorting intermittently as the engine vibrates.
__________________
Dave
Snarkiness without knowledge is, well, just sad, really.



Sherlyn Popelka DUI, Aggravated Assault, Fugitive Arrest Reports HERE:
http://www.sherlynpopelka.net/
MegaGlide is offline   Reply With Quote Quick reply to this message
Old 09-22-2009, 10:28 AM   #3 (permalink)
Altered States
 
Waffen's Avatar
 
Join Date: Jun 2004
Location: Colorado
Posts: 6,258
Waffen is reading this now saying WTF is this?
Manifold leak, carb jets plugged up with some debris.


W
Waffen is offline   Reply With Quote Quick reply to this message
Old 09-22-2009, 10:35 AM   #4 (permalink)
Seasoned Rider
 
JoeShovel's Avatar
 
Join Date: Aug 2008
Location: NC
Posts: 59
JoeShovel wants to know Dino or Syn?
Quote:
Originally Posted by Waffen View Post
Manifold leak, carb jets plugged up with some debris.


W
How would I go about cleaning this?
__________________
1973 FX frame chopped in the rear with rigid welded in place. Bottom end is 58 panhead topped with 66 shovelhead. S&S super E carb, Andrew B grind cam. 73 4spd trans. Kick and Electric start... A bobber fo sho
JoeShovel is offline   Reply With Quote Quick reply to this message
Old 09-23-2009, 08:54 AM   #5 (permalink)
Banned
 
Join Date: Dec 2003
Location: Munnsville NY
Posts: 4,509
Hillside wants to know Dino or Syn?
NAPA sells a good carb cleaner kit. Very agressive cleaning solution.
Scott
Hillside is offline   Reply With Quote Quick reply to this message
Old 09-23-2009, 12:04 PM   #6 (permalink)
Altered States
 
Waffen's Avatar
 
Join Date: Jun 2004
Location: Colorado
Posts: 6,258
Waffen is reading this now saying WTF is this?
Quote:
Originally Posted by JoeShovel View Post
How would I go about cleaning this?

First to the manifold. If you can get it running, spray some WD40 where the manifold is bolted to the jugs. If you notice a change in idle or how it runs you may have a leak which creates a lean environment which you experience as the backfiring through the carb.

To clean the carb, personally I think it's best to take it off the bike, pull it apart and clean it throughly and don't forget to check the float.

I don't know your carb specifically but you should be able to find a manual showing the schematics which will help. Also if you do take the carb apart it might be a good idea to change the o rings and gaskets.

W
Waffen is offline   Reply With Quote Quick reply to this message
Old 09-24-2009, 07:48 AM   #7 (permalink)
Seasoned Rider
 
JoeShovel's Avatar
 
Join Date: Aug 2008
Location: NC
Posts: 59
JoeShovel wants to know Dino or Syn?
Could anything else besides this create a backfire though.... I guess I'm just worried that I have a stuck valve or something...

I was informed that:

backfire though pipes = carb

backfire through carb = ignition.

Is this true?
__________________
1973 FX frame chopped in the rear with rigid welded in place. Bottom end is 58 panhead topped with 66 shovelhead. S&S super E carb, Andrew B grind cam. 73 4spd trans. Kick and Electric start... A bobber fo sho
JoeShovel is offline   Reply With Quote Quick reply to this message
Old 09-24-2009, 11:12 AM   #8 (permalink)
Altered States
 
Waffen's Avatar
 
Join Date: Jun 2004
Location: Colorado
Posts: 6,258
Waffen is reading this now saying WTF is this?
Quote:
Originally Posted by JoeShovel View Post
Could anything else besides this create a backfire though.... I guess I'm just worried that I have a stuck valve or something...

I was informed that:

backfire though pipes = carb, Rich condition to much gas valves possible

backfire through carb = ignition. Lean condition, leak, plugged jet, jetted incorrectly and quite possibly ignition.

Is this true?
Timing might also be off.


W
Waffen is offline   Reply With Quote Quick reply to this message
Old 09-24-2009, 01:12 PM   #9 (permalink)
Seasoned Rider
 
JoeShovel's Avatar
 
Join Date: Aug 2008
Location: NC
Posts: 59
JoeShovel wants to know Dino or Syn?
Quote:
Originally Posted by Waffen View Post
Timing might also be off.


W
Ok, this is something I was also thinking but should I advance or retard...?

I would think by retarding it, it would still be too lean if that is the case.
__________________
1973 FX frame chopped in the rear with rigid welded in place. Bottom end is 58 panhead topped with 66 shovelhead. S&S super E carb, Andrew B grind cam. 73 4spd trans. Kick and Electric start... A bobber fo sho
JoeShovel is offline   Reply With Quote Quick reply to this message
Old 09-24-2009, 06:07 PM   #10 (permalink)
OUCH! That hurt
 
wfolarry's Avatar
 
Join Date: Jan 2007
Location: Oak Lawn, IL.
Posts: 667
wfolarry wants to know Dino or Syn?
Putting in 87 octane could make it backfire as it would appear to be lean. Putting premium in should have solved this. Did you do anything else [play with timing, jets etc.] when it was backfiring to try & correct it before you took it apart?
__________________
38 years of ridin' & wrenchin'
wfolarry is offline   Reply With Quote Quick reply to this message
Old 09-28-2009, 09:41 AM   #11 (permalink)
Seasoned Rider
 
JoeShovel's Avatar
 
Join Date: Aug 2008
Location: NC
Posts: 59
JoeShovel wants to know Dino or Syn?
Well it was 89 octane that I put in it and drained it all out and put in fresh 93. Now, when I was stuck on the side of the road I did play with timing but have since put it back to where it was. It is very hard to start now. Have not had the time to play with it that much this weekend. Hopefully more this week since it is going to be nice.
__________________
1973 FX frame chopped in the rear with rigid welded in place. Bottom end is 58 panhead topped with 66 shovelhead. S&S super E carb, Andrew B grind cam. 73 4spd trans. Kick and Electric start... A bobber fo sho
JoeShovel is offline   Reply With Quote Quick reply to this message
Old 10-01-2013, 06:20 AM   #12 (permalink)
FNG :)
 
Join Date: Sep 2013
Location: Ohio
Posts: 12
Ltsulli1 wants to know Dino or Syn?
Check to make sure your stator and rotor is charging the bike... With the bike running put a meter on your battery and rev it up to about 2k rpm watch the meter and make sure the voltage spikes up to around 12.9vdc if it doesn't move then your stator is bad or your regulator... No way to test regulator but you can test the stator by pulling the plug off the motor where the regulator plug into it.... You should have continuity between both posts of stator... Then each post to ground should have no continuity if it does anything different your state or is bad! Good luck
Ltsulli1 is offline   Reply With Quote Quick reply to this message
Old 10-01-2013, 08:28 AM   #13 (permalink)
VTF Site Sponsor
 
springer-'s Avatar
 
Join Date: Mar 2005
Location: Maine
Posts: 9,970
springer- is still riding a stock bike springer- is still riding a stock bike
Quote:
Originally Posted by Ltsulli1 View Post
Check to make sure your stator and rotor is charging the bike... With the bike running put a meter on your battery and rev it up to about 2k rpm watch the meter and make sure the voltage spikes up to around 12.9vdc if it doesn't move then your stator is bad or your regulator... No way to test regulator but you can test the stator by pulling the plug off the motor where the regulator plug into it.... You should have continuity between both posts of stator... Then each post to ground should have no continuity if it does anything different your state or is bad! Good luck
This thread is 4 years old. I hope he has it fixed by now.
__________________
What do I know, I ride a Shovel


Check out Ride of the Month






207-621-8089
springer- is offline   Reply With Quote Quick reply to this message
Old 10-02-2013, 08:14 AM   #14 (permalink)
FNG :)
 
Join Date: Sep 2013
Location: Ohio
Posts: 12
Ltsulli1 wants to know Dino or Syn?
But there are always people with simalar problems just hoping to help the next person is all!
Ltsulli1 is offline   Reply With Quote Quick reply to this message
Old 10-19-2013, 05:09 AM   #15 (permalink)
FNG :)
 
Join Date: Oct 2013
Location: Easton, Pa.
Posts: 14
Billyroyjoebobj wants to know Dino or Syn?
new to forum, Your exactly right about others having this problem. It is the same thing i've been going through. Differences are I built my bike to look like a '58. It's on a '66 frame ('53 fle w/std heads & s&s super e. Thanks for tips. will get on with it this weekend.
Billyroyjoebobj is offline   Reply With Quote Quick reply to this message
Sponsored Links
Advertisement
 
Reply

Quick Reply
Message:
Options

Register Now

In order to be able to post messages on the V-Twin Forum : Harley-Davidson Motorcycle Forums 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. WE WILL SEND A CONFIRMATION EMAIL TO THE ADDRESS YOU PROVIDE. If the email address is NOT VALID, you will not be given access to the system!
Email Address:

Log-in

Human Verification

In order to verify that you are a human and not a spam bot, please enter the answer into the following box below based on the instructions contained in the graphic.



Thread Tools
Display Modes

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 Off
Pingbacks are Off
Refbacks are On


Powered by vBadvanced CMPS v3.2.2

All times are GMT -5. The time now is 06:24 AM.


Powered by vBulletin® Copyright ©2000 - 2014, Jelsoft Enterprises Ltd.
Content Relevant URLs by vBSEO 3.6.0
(C)2001-2012 V-twinForum.com All Rights Reserved (C)2001- V-twinForum.com All Rights Reserved
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 Ninja H2 Forum Ducati Scrambler Forum