Choke Issues on a carb
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1st Gear
Joined: Jan 2018
Posts: 5
Likes: 0
From: Hampton Roads
Choke Issues on a carb
Thanks for everyone's help ahead of time!
I am having idling problems with my 2003 sportster that has only 3,800 miles on it. I have already broken down the carb as far as you can and cleaned it. The internals of the carb are all stock at this time but I am willing to modify if that will fix the problem. The plug for the Idle Mixture Adjustment Screw has already been removed and the screw is currently at 2 3/4 turn down after seating it all the way in. I originally had the screw at 2 1/2 but then the idle was really rough. I have posted 2 videos for review. One is the bike idling after a 30 min ride from the pipes and the other is right after that but showing the problems with the choke.
I am having idling problems with my 2003 sportster that has only 3,800 miles on it. I have already broken down the carb as far as you can and cleaned it. The internals of the carb are all stock at this time but I am willing to modify if that will fix the problem. The plug for the Idle Mixture Adjustment Screw has already been removed and the screw is currently at 2 3/4 turn down after seating it all the way in. I originally had the screw at 2 1/2 but then the idle was really rough. I have posted 2 videos for review. One is the bike idling after a 30 min ride from the pipes and the other is right after that but showing the problems with the choke.
Last edited by specsphere; Sep 8, 2019 at 12:04 AM.
Ultimate HDF Member
Joined: Aug 2010
Posts: 5,014
Likes: 739
From: Northern California
Good checklist to troubleshoot carb issues here http://nightrider.com/biketech/carb_troubleshooting.htm NOTE THE SECTION "POOR IDLING"
Good info here regarding carb operation and diagnostics http://xlforum.net/forums/showthread.php?t=642408
And here
Good info here regarding carb operation and diagnostics http://xlforum.net/forums/showthread.php?t=642408
And here
Last edited by mmesa005; Sep 8, 2019 at 04:02 AM.
Twiddlers
The first thing to do is replace Throttle Stop and Pilot Air screws with " Thumbscrews " then you can stop for a twiddle with the engine running whenever you want . You might want to order a new carb to manifold gasket as well .
I'd go with that .
Advanced
Joined: Oct 2018
Posts: 77
Likes: 22
From: Canada
It's obviously very lean, if it won't run without the enrichener pulled out. Could be fuel supply is blocked (petcock screen, old fuel hose collapsed, partial vacuum leak on the petcock vacuum line). It could be your float level is set too low (did you set your float level to spec?). Could be intake leaks causing it to run lean, (intake seals, carb to intake seal, cracked vacuum lines). How does it run off idle? What RPM are you idling at? Should be around 950-1000 RPM. What condition are your plugs in? Usual way to set the idle mixture screw is to have a warm engine. Turn it in until it stumbles. Turn it out until it stumbles. Set it half way between those 2 points. If it won't run without the enrichener pulled you can't set the idle mixture though. You are probably a little rich at 2 3/4 out stock, but it should run. Something else is not right. 3800 miles on an 03 means it has been sitting a lot. You have to make sure all those little jet orifices are cleaned out of any varnish and/or dirt.
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Club Member
Joined: Jun 2007
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From: Bedford UK
When dismantling your carb, did you buy and install a rebuild kit? On such an old carb rubber parts inside, for example, may be past their best. A kit comes with new rubber parts, gaskets etc. The diaphragm on the slide can also perish or be damaged if not handled with kid gloves.
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Seasoned HDF Member
Joined: Aug 2006
Posts: 24,526
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From: Pennsylvania
Your post back in 2018 on the same issue stated you had 3,300 miles on the Sportster, this post states you have 3,800 miles on this bike now. That is only 500 miles, probably be good if you put some fuel cleaner in the gas tank and run it for about 3 tankfuls. May have old gas with water in the tank. Have you drained the tank, checked the petcock and tried new fuel? A little water will cause many idling issues.
Sportsters do not like to sit around, they like to be run, hot and hard. Get out and have some fun.
Sportsters do not like to sit around, they like to be run, hot and hard. Get out and have some fun.
Road Master
Joined: Sep 2010
Posts: 1,077
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First things first, check for any vacuum leaks; vacuum hoses, carb to intake seal (doughnut), petcock, etc.
If you're SURE there's no vacuum leaks then you have a plugged jet or something in the carb. Not running without the choke is classic 'too lean' symptom.
If you're SURE there's no vacuum leaks then you have a plugged jet or something in the carb. Not running without the choke is classic 'too lean' symptom.