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Old 03-10-2012, 06:49 AM   #1 (permalink)
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Carb popping

I've had this issue since I bought my bike new. I have a 05 1200C since adding Screaming Eagle slip on and having it rejetted by a harley service shop, it's backfiring thru the carberator, only on take off. More if it's running hot. Is this common? Has anyone figured it out? Could it be timing? I don't know anymore.. Frustrating.. The Harley service tech told me it's a sportster thing. They all do it and there's nothing they can do about it.
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Old 03-10-2012, 08:34 AM   #2 (permalink)
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FXRS84 wants to know Dino or Syn?
what kinda carb.. does it happen after it is warmed up....
Often techs have their set ups and do not go through the " ride it check the plugs"
method, as known as the chop method. check out a coupla articles , and check it
yourself

www.harley-performance.com www.nightrider.com

I have some others specific to different carbs, Kehien butterfly or CV, S&S
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Old 03-10-2012, 08:44 AM   #3 (permalink)
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Nitram_b4 is reading this now saying WTF is this?
Has the plug been removed from the mixture screw?
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Old 03-10-2012, 08:45 AM   #4 (permalink)
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Nitram_b4 is reading this now saying WTF is this?
try reading this info
http://www.nightrider.com/biketech/hd_cv_mods.htm
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Old 03-10-2012, 11:36 PM   #5 (permalink)
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If it weren't a self-adjusting valve engine I'd say it's a poorly adjusted valve (backfiring through the carb is a tell-tale symptom on metrics with poorly adjusted valves). Is it possible that could be the issue? Something causing the valves not to be where they should be?
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Old 03-11-2012, 12:32 AM   #6 (permalink)
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Waffen is reading this now saying WTF is this?
Could be timing, but popping through the carb can also mean a lean condition. Wrong jets, leak at intake..


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Old 03-11-2012, 05:07 AM   #7 (permalink)
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Sounds Lean to me .. If don't know how to adjust the Carb or change the Screws Find a Good Indy .. Owned Lots of Sportsters and is not a Sportster thing to backfire through the Carb although they will do it if the Carb ain't right .. If all you did was switch pipes should be able to just richen it a little without changing jet sizes ..
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Old 03-11-2012, 06:42 AM   #8 (permalink)
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Carb is stock never been opened other then doing jets by a Harley tech. Ill have to check out a few of these possibilities you guy have suggested. Thanks for the help and ill let you know my progress.
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Old 03-11-2012, 10:01 AM   #9 (permalink)
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My 2006 1200 custom does the same thing. Running premium fuel helped a lot and "burping" the engine before taking off does, too. I just give it a little throttle blip after idling at a stop light to clean it out before taking off.

The bikes run lean and you'll pay an MPG price if you enrich the mixture to eliminate the carb coughing.

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Old 04-14-2012, 05:56 AM   #10 (permalink)
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Think I got it. Thanks for all your help and suggestions. I took the carb off, cleaned it thoroughly inside and out. I had been told to remove 3 coils on the slide spring to reduce restriction and get better throttle response. Also polished the slide and intake opening till it shinned like a mirror, also for less air restriction. Main jet is a 170, turned the mixture screw 1/8 of a turn richer. And used Autolite plugs instead of screaming eagle plugs. Made all the differance. Thanks again for all the help.
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Old 04-14-2012, 12:43 PM   #11 (permalink)
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your 1st mistake is letting a Harley Dealer touch your bike! Go to CV Performance.com and read and or contact them and get a upgrade performance kit to make that carb work right...again this is a good carb and a XL or BigTwin can make 80 + HP with it All CV carbs are way to lean period you might want to replace the rubber boot the carb is pushed into Rubber does get funky from heat and oil and vibration or you can send the carb to a place that is on ebay motors under cv carbs and he blueprints the carb for $189 ! One big mistake ma lot of Harley owners do when they start there CV equiped bikes is use the enrichner [aka choke] as a fast idle when the motor is cold...start the bike....set the thumbscrew @ the throttle above 1000 rpm...and push that choke back in ASAP saves gas and fouled plugs
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