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carb coughing and running on

Discussion in 'CV Performance' started by shay engesether, May 15, 2015.

  1. shay engesether

    shay engesether Active Member

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    I gave my 05 883 sportster the full treatment of CVP carb parts after buying the bike a few months ago and im having a hard time getting rid of a cough thru the carb and the bike staying running for a second or so after hit the cut off switch.

    I bought the bike not running, as it had sat for 3 years with old gas in it and the carb was FILTHY. I cleaned the living day lights out of it and believe i got it clean enough. I followed the passage cleaning instruction on CVP's website as well. I installed a new: CVP slide needle, EZ-just mixture screw, emulsion tube, #42 idle jet, #170 main jet, vaccum slide (un-drilled), 4 sided float valve (HD part), accelerator pump nozzle, slide spring, and idle adjustment screw. I also followed the installation instructions...float valve is set correctly, needle jet in correctly etc..

    But for some reason, and i can't always duplicate it, a quick blip of the throttle from idle will cause the carb to cough..it does it some times on decel too...i've tried adjusting the EZ-just but i have lost track and can't remember how many turns i am at. The EZ just seated with 2 threads still showing, and i am at 5 threads showing now...i think more is going on then that because of the running on after the cut off switch is off.

    Another thing worth mentioning is the CVP accelerator pump makes a messy plume of fuel the throttle is blipped with the air cleaner off. I have the nozzle pointed right to the side of the slide needle as before it was hitting the needle. I also pressed the pump in with less than 1/16" gap between it and the carb bowl. The plume of fuel blows backwards sometimes...not sure if this is a problem when the bike is moving and air is flowing through the air box pushing that plume back in..?

    Ok, i've ranted long enough..im at a lost as to what could be the problem..any suggestions?
  2. shay engesether

    shay engesether Active Member

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    forgot to mention..the bike runs great otherwise..no coughing while shifting through gears, even when im getting on it.
  3. kenfuzed

    kenfuzed Administrator Staff Member

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    Could be a number of things.
    1) Missing check valve under accelerator pump nozzle, causing excess pump spray.
    2) Worn or bent throttle plate which can increase engine run-on.
    3) Idle set too high.
    4) Timing issue.
    5) Worn valves.
    6) Exhaust leak at exhaust port.
    7) Bad crank position sensor.
    8) Faulty wires (MAP sensor, etc)

    I would start by pulling the trouble codes to first locate any existing problems. Properly tuning the carburetor can be futile if ignition timing, faulty sensors, or electrical conditions are not correct beforehand.
  4. shay engesether

    shay engesether Active Member

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    i heard the check ball for the accelerator pump rattling around, and could see it when i was replacing the nozzle, so that should be good. I was having a hard time finding actual idle speed as my timing light i use is very jumpy but it belive its somewhere between 950-1050 rpm.

    There are no trouble codes, atleast the check engine light has never lit up except when the key is first turned on, then the light goes out. The bike doesn't even have 2k miles on it yet, so i would hope nothing is worn out yet!

    I checked for intake leaks with propane throughly and didn't find any
  5. kenfuzed

    kenfuzed Administrator Staff Member

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    Don't rely on the check engine light for trouble codes. A very common problem on 2004-newer Sportsters was a faulty crank sensor (CKP) and there was actually a recall on some. Intermittent sensor problems will not show the check engine light until something has permanently failed. You must run the self diagnostics built into your odometer to read through any and all codes that the ECM has saved in memory. Here is a description of that procedure:
    http://www.cv-performance.com/harley-diagnostic-trouble-codes/
    P0373 and P0374 are the common codes found when the CKP is intermittently failing.

    If in doubt about trouble codes it is recommended to have a qualified Harley tech scan the codes with the factory tool. The "jumpy" RPMs you read could be of a concern and point to issues with either the ignition system or deeper troubles with a bad or worn valve. This is beyond the scope of what can be diagnosed through a forum post and may be worth the extra money to have the bike looked at professionally. A qualified tech and shop with the right diagnostic tools could pinpoint the problem quickly and perhaps identify any potential problem that is lurking that could cause a much bigger failure further down the road.
  6. shay engesether

    shay engesether Active Member

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    read the codes, there are none. My timing light uses an inductive pick up for rpm, i attribute the jumpiness to mechanical "noise" from the bike..as its a little jumpy when used on a car as well.
  7. shay engesether

    shay engesether Active Member

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    where would 5 threads exposed (how many turns) on the EZ-just put me in terms of mixture adjustment? somewhere in the ball park? maybe i haven't leaned it out enough yet?
  8. hotroadking

    hotroadking Super Moderator Staff Member

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    You don't go by threads you go by turns from bottom
    It should be about 2 to 2.5 turns from all the way in then back

    Gently turn it in and lightly bottom the screw, then back out 2.5 turns
  9. FLHTbiker

    FLHTbiker Moderator Staff Member

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    I usually back mine out 2 turns and adjust from there. My 03 Heritage Springer is adjusted at 1-3/4 turns and runs perfect. I sometimes like the old carb better then the new fuel injection bikes.
  10. shay engesether

    shay engesether Active Member

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    Took the air cleaner off and started it up, when I blip the throttle the stream from the accelerator nozzle hits the throttle plate, breaks up and puddles in the carb as well as makes a mist the blows backwards. Im thinking this is causing puddling in the carb and is causing the cough and run on..? I have the pump nozzle nearly bottomed out, but it still sprays upwards..kinda hits the slide needle too

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