The Sportster and Buell Motorcycle Forum - The XLFORUM®
 

Go Back   The Sportster and Buell Motorcycle Forum - The XLFORUM® > SPORTSTER MOTORCYCLE FORUM > Sportster Motorcycle Era Specific and Model Specific > Ironhead Sportster Motorcycle Talk (1957-1985)
XLF Blogs XLF Arcade XLF Disclaimer/Privacy Statement/Terms Of Use

Notices

Ironhead Sportster Motorcycle Talk (1957-1985) For all those that wanna talk about Ironhead Sportster Motorcycles

Active Threads
0 Cam chest vent fitting
Last Post: bustert
Posted On: 1 Minute Ago
Replies: 3
Views: 254
0 Issues with progressive springs
Last Post: APJ CUSTOMS
Posted On: 1 Minute Ago
Replies: 4
Views: 74
5 1200 or 883
Last Post: Folkie
Posted On: 2 Minutes Ago
Replies: 1,240
Views: 366,019
0 What did you do for your sporty Today?
Last Post: boomerguy
Posted On: 3 Minutes Ago
Replies: 7,209
Views: 1,058,964
0 top end rebuild
Last Post: Ferrous Head
Posted On: 5 Minutes Ago
Replies: 85
Views: 4,573
0 Vulcan Mid Glide Triple Tree Conversion Set
Last Post: Dariusz
Posted On: 10 Minutes Ago
Replies: 4
Views: 137
0 Sportster 48 in a Nighster
Last Post: Dariusz
Posted On: 11 Minutes Ago
Replies: 4
Views: 122
0 Do not buy this oil!
Last Post: Crusty
Posted On: 20 Minutes Ago
Replies: 56
Views: 2,269
0 Keep & Kill
Last Post: Graywolf
Posted On: 23 Minutes Ago
Replies: 18,427
Views: 1,094,522
0 Ironhead Exhaust Poll
Last Post: Ferrous Head
Posted On: 26 Minutes Ago
Replies: 196
Views: 56,036
0 Hot Chicks on Hot Bikes
Last Post: Graywolf
Posted On: 33 Minutes Ago
Replies: 11,230
Views: 2,230,437
0 Iree's late night cafe
Last Post: ~Grind~
Posted On: 42 Minutes Ago
Replies: 1,740
Views: 240,007
0 Shock search is OVER !!!
Last Post: XL1275
Posted On: 42 Minutes Ago
Replies: 2
Views: 64
0 Early Sportster XLCH 900 Dyno Run
Last Post: Heff
Posted On: 52 Minutes Ago
Replies: 114
Views: 32,881
0 Oil leaking
Last Post: Zari
Posted On: 1 Hour Ago
Replies: 22
Views: 899
0 IH Crankcase Pressure and Engine Breathing
Last Post: thefrenchowl
Posted On: 1 Hour Ago
Replies: 101
Views: 4,542
0 excellent color
Last Post: mick42
Posted On: 1 Hour Ago
Replies: 13
Views: 695
0 Official XL Forum Random Image Thread (NO NUDITY!)
Last Post: Stairman
Posted On: 2 Hours Ago
Replies: 48,661
Views: 7,874,028
0 Food porn
Last Post: Stairman
Posted On: 3 Hours Ago
Replies: 2,122
Views: 423,237
0 Hottie of the day, no nudity.
Last Post: Stairman
Posted On: 3 Hours Ago
Replies: 23,324
Views: 2,379,171
0 Clutch blow up
Last Post: Tonimacaroni
Posted On: 4 Hours Ago
Replies: 14
Views: 386
0 New oil tank
Last Post: npaisnel
Posted On: 5 Hours Ago
Replies: 127
Views: 5,977
0 weight loss thread
Last Post: catpepper
Posted On: 5 Hours Ago
Replies: 67
Views: 25,638
0 Transformer XR1200
Last Post: Davo_137
Posted On: 6 Hours Ago
Replies: 486
Views: 56,044
0 My frist question...Fork seal replacement
Last Post: brucstoudt
Posted On: 7 Hours Ago
Replies: 10
Views: 412
0 Fork seal follow up...Stop me if I'm being stupid.
Last Post: brucstoudt
Posted On: 7 Hours Ago
Replies: 4
Views: 159
0 my daily driver
Last Post: 84rzv500r
Posted On: 10 Hours Ago
Replies: 3
Views: 1,198
0 my sunday driver...
Last Post: 84rzv500r
Posted On: 10 Hours Ago
Replies: 10
Views: 3,313
0 compression test question
Last Post: sportsterdoc
Posted On: 11 Hours Ago
Replies: 15
Views: 203
0 Cruising RPMs
Last Post: 1200CustomHD
Posted On: 11 Hours Ago
Replies: 97
Views: 7,142
More...
Members Birthdays
seajay, Hugh Betcha (74), jimhd89 (71), JayFL459 (71), Big Al (64), dakota_dj (63), 10walt (61), kiltbill (61), timsvalk (60), horsewriter (55), Benetampa (43), hobson8494 (36), Joker8494 (36), 8ball (31)
Reply
 
Share Thread Tools Display Modes
  #1  
Old 1 Week Ago
steve lewis steve lewis is offline
XL FORUM TEAM MEMBER
 
Join Date: Oct 2013
Posts: 67
Sportster/Buell Model: 1972 xlch
Sportster/Buell Year: 1972
Reputation: 1215
steve lewis has a spectacular aura aboutsteve lewis has a spectacular aura aboutsteve lewis has a spectacular aura aboutsteve lewis has a spectacular aura aboutsteve lewis has a spectacular aura aboutsteve lewis has a spectacular aura aboutsteve lewis has a spectacular aura aboutsteve lewis has a spectacular aura aboutsteve lewis has a spectacular aura about
Default stumble

72 ch, bendix carb, starts great, idles fine , As soon as I accelerate, motor stumbles and back fires though the exhaust. At speed , 40mph, smooth, If I accelerate, stumble and back fire. I have read every post in can read, New battery, new points , new plugs, new wires, new coil, old condenser, new fuel filter, I restored the bike 5 years ago, and have not ridden it much. Never did anything to the carb, so should I rebuild the carb, I am thinking dirt or grim. Also tested intake for leaks with propane. Tight. I have the FM from 72, Any suggestions, or guidance, or any help what so ever would be great. steve
Reply With Quote
  #2  
Old 1 Week Ago
The Doctor71 The Doctor71 is online now
Senior Chief Know It All
 
Join Date: Mar 2010
Location: Toronto, Ontario
Posts: 825
Sportster/Buell Model: xlch
Sportster/Buell Year: 1971
Sportster/Buell Model #2: xlh
Sportster/Buell Year #2: 1974
Other Motorcycle Model: xl1200cp
Other Motorcycle Year: 2011
The Doctor71 has disabled reputation
Default

It wouldn't surprise me if you had multiple things going on.... but where to start ? My troubleshooting 101 philosophy starts with..... (in a word)

Ignition. I'd suggest read & follow the pointers in this thread..... http://xlforum.net/forums/showpost.p...05&postcount=9

Get your ignition on the money first.... then follow the evidence to the next problem. Your motor will tell you what to do next.
Reply With Quote
  #3  
Old 1 Week Ago
wedge's Avatar
wedge wedge is offline
XL FORUM TEAM MEMBER
 
Join Date: Jun 2010
Posts: 11,810
Sportster/Buell Model: 1200R
Sportster/Buell Year: 2005
Other Motorcycle Model: 5 bikes and 1 quad
Reputation: 6307555
wedge has a reputation beyond reputewedge has a reputation beyond reputewedge has a reputation beyond reputewedge has a reputation beyond reputewedge has a reputation beyond reputewedge has a reputation beyond reputewedge has a reputation beyond reputewedge has a reputation beyond reputewedge has a reputation beyond reputewedge has a reputation beyond reputewedge has a reputation beyond repute
Default

I agree that the ignition should be tuned first. After that and assuming the problem is still there then yes I would get serious about the carb. Could be the accelerator pump shot is either not there or it could be anemic. The backfire is a typical sign of going lean. The jets could just be plugged some too. Could also have an air leak at the manifold. You can see the accelerator pump shot by just looking in the throat of carb and snapping the throttle. It should shoot straight at the needle.
__________________
A Biker is not just any guy who rides... that's a motorist.
A guy that gets up and rides again after every crash... that's a Biker.

Whitworth Fork Brace: http://xlforum.net/forums/m...outme&simple=1
Reply With Quote
  #4  
Old 1 Week Ago
sportsterdoc's Avatar
sportsterdoc sportsterdoc is offline
Senior Master Custom Bike Builder
 
Join Date: Apr 2012
Location: Mojave Desert
Posts: 13,754
Sportster/Buell Model: 1200S
Sportster/Buell Year: 2002
Sportster/Buell Model #2: XLH883
Sportster/Buell Year #2: 2003
Reputation: 6722851
sportsterdoc has a reputation beyond reputesportsterdoc has a reputation beyond reputesportsterdoc has a reputation beyond reputesportsterdoc has a reputation beyond reputesportsterdoc has a reputation beyond reputesportsterdoc has a reputation beyond reputesportsterdoc has a reputation beyond reputesportsterdoc has a reputation beyond reputesportsterdoc has a reputation beyond reputesportsterdoc has a reputation beyond reputesportsterdoc has a reputation beyond repute
Default

Not familiar with the Bendix, but if it has an accelerator pump, that would be my first check...and I usually pay most attention to electrical issues.
Reply With Quote
  #5  
Old 1 Week Ago
doodah man's Avatar
doodah man doodah man is online now
Senior Master Custom Bike Builder
 
Join Date: May 2009
Location: 37° 25' 28" N by -80° 03' 42" W
Posts: 10,948
Sportster/Buell Model: XLCH
Sportster/Buell Year: 1975
Reputation: 859293
doodah man has a reputation beyond reputedoodah man has a reputation beyond reputedoodah man has a reputation beyond reputedoodah man has a reputation beyond reputedoodah man has a reputation beyond reputedoodah man has a reputation beyond reputedoodah man has a reputation beyond reputedoodah man has a reputation beyond reputedoodah man has a reputation beyond reputedoodah man has a reputation beyond reputedoodah man has a reputation beyond repute
Default

"old condenser" could be an issue.
__________________
"when you don't know where you're going, any road'll take you there"
Reply With Quote
  #6  
Old 1 Week Ago
wedge's Avatar
wedge wedge is offline
XL FORUM TEAM MEMBER
 
Join Date: Jun 2010
Posts: 11,810
Sportster/Buell Model: 1200R
Sportster/Buell Year: 2005
Other Motorcycle Model: 5 bikes and 1 quad
Reputation: 6307555
wedge has a reputation beyond reputewedge has a reputation beyond reputewedge has a reputation beyond reputewedge has a reputation beyond reputewedge has a reputation beyond reputewedge has a reputation beyond reputewedge has a reputation beyond reputewedge has a reputation beyond reputewedge has a reputation beyond reputewedge has a reputation beyond reputewedge has a reputation beyond repute
Default

Quote:
Originally Posted by doodah man View Post
"old condenser" could be an issue.
Not likely, capacitors either work or they don't, and when they don't they burn points almost immediately because their sole purpose in life is to eliminate the arc from points opening. Kind of like a sponge for catching the arc. You are better off not replacing a capacitor that is working, because it's more likely for a new one to fail right out of the box than have a good working one fail.
Reply With Quote
  #7  
Old 1 Week Ago
randy3934's Avatar
randy3934 randy3934 is offline
Senior Custom Bike Builder
 
Join Date: Dec 2011
Location: under a roof
Posts: 2,969
Sportster/Buell Model: xlh 1000 69 79 xlch
Sportster/Buell Year: 1977
Sportster/Buell Model #2: 80 FXE 82FLH 83FXR
Other Motorcycle Model: 78FLH 79xlch 96xl 79xlh
Reputation: 152122
randy3934 has a brilliant futurerandy3934 has a brilliant futurerandy3934 has a brilliant futurerandy3934 has a brilliant futurerandy3934 has a brilliant futurerandy3934 has a brilliant futurerandy3934 has a brilliant futurerandy3934 has a brilliant futurerandy3934 has a brilliant futurerandy3934 has a brilliant futurerandy3934 has a brilliant future
Default

I'm thinking drag pipes
__________________
I'm not a complete idiot, some parts are missing. not enough room to list all my harleys.
Reply With Quote
  #8  
Old 1 Week Ago
sportsterdoc's Avatar
sportsterdoc sportsterdoc is offline
Senior Master Custom Bike Builder
 
Join Date: Apr 2012
Location: Mojave Desert
Posts: 13,754
Sportster/Buell Model: 1200S
Sportster/Buell Year: 2002
Sportster/Buell Model #2: XLH883
Sportster/Buell Year #2: 2003
Reputation: 6722851
sportsterdoc has a reputation beyond reputesportsterdoc has a reputation beyond reputesportsterdoc has a reputation beyond reputesportsterdoc has a reputation beyond reputesportsterdoc has a reputation beyond reputesportsterdoc has a reputation beyond reputesportsterdoc has a reputation beyond reputesportsterdoc has a reputation beyond reputesportsterdoc has a reputation beyond reputesportsterdoc has a reputation beyond reputesportsterdoc has a reputation beyond repute
Default

Quote:
Originally Posted by wedge View Post
Not likely, capacitors either work or they don't, and when they don't they burn points almost immediately because their sole purpose in life is to eliminate the arc from points opening. Kind of like a sponge for catching the arc.
In over 50 years of wrenching, I only found one bad 0.22 mfd capacitor.
It was on a positive ground MG.
One spark, then no more.

It is possible for the foil layers to short, as with a coil, but very rare.

Motor start capacitors are used for starting surge and run capacitors for efficiency.

Ignition point capacitors actually have a dual purpose:

1. As Wedge already stated, to reduce the effects of arcing as points open. Interrupting DC is not as easy as AC, since there is no sine wave going to zero 60 times per second. So the capacitor (condenser) absorbs that.

2. When the points close, to energize the coil quickly.
Reply With Quote
  #9  
Old 1 Week Ago
steve lewis steve lewis is offline
XL FORUM TEAM MEMBER
 
Join Date: Oct 2013
Posts: 67
Sportster/Buell Model: 1972 xlch
Sportster/Buell Year: 1972
Reputation: 1215
steve lewis has a spectacular aura aboutsteve lewis has a spectacular aura aboutsteve lewis has a spectacular aura aboutsteve lewis has a spectacular aura aboutsteve lewis has a spectacular aura aboutsteve lewis has a spectacular aura aboutsteve lewis has a spectacular aura aboutsteve lewis has a spectacular aura aboutsteve lewis has a spectacular aura about
Default

Thanks Guys,
Reply With Quote
  #10  
Old 1 Week Ago
wedge's Avatar
wedge wedge is offline
XL FORUM TEAM MEMBER
 
Join Date: Jun 2010
Posts: 11,810
Sportster/Buell Model: 1200R
Sportster/Buell Year: 2005
Other Motorcycle Model: 5 bikes and 1 quad
Reputation: 6307555
wedge has a reputation beyond reputewedge has a reputation beyond reputewedge has a reputation beyond reputewedge has a reputation beyond reputewedge has a reputation beyond reputewedge has a reputation beyond reputewedge has a reputation beyond reputewedge has a reputation beyond reputewedge has a reputation beyond reputewedge has a reputation beyond reputewedge has a reputation beyond repute
Default

Thanks Jerry. I tend to forget your point #2.

In practice, like yourself I can only remember finding one bad capacitor and if memory serves correctly, it was the same as you describe, no spark at all from the coil. My assumption is that it must have been internally shorted to ground.

Back in 72-75 I worked for American Optical in New Hampshire and I used to do sample testing on the electronic parts we brought in. That is where I saw a large number of capacitors that were bad from the factory. After that, as a Mechanic I quit replacing condensers automatically with a tune up.

Bottom line here Steve is that the backfire is leading us in the direction of the bike going lean when you hit the throttle.
Reply With Quote
Reply

Bookmarks


Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
 
Thread Tools
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 Off

Forum Jump



All times are GMT +1. The time now is 14:18.


Powered by vBulletin® Version 3.8.11
Copyright ©2000 - 2020, vBulletin Solutions Inc.
XL Forum® - Linson Media LLC