Sportster Carb or Fuel issue

Discussion in 'Engine, Fuel and Exhaust' started by dlclay, Sep 7, 2010.

  1. dlclay

    dlclay New Member

    Hi from the new guy,

    Searched for an hour for something relating to my issue. Now I will post.

    I have a 2005 883 HD Sportster. Had it for a year. It sat in the garage for the winter while the military sent me off to the great unknown. Came home in the spring, started fine but after getting warmed up it would cut out when coming to a stop and be difficult to start. I thought it was overheated as I have to wait in line to get on base through the gate.

    Then it got worse. It starts and runs fine from a cold start. As soon as it get warm it stalls at idle speeds. So I stoped driving it as it stalls all the time and make like inconvienant waiting to start it to drive five feet and cut out. Thought it was bad fuel and gummed up carb.

    Well, after a couple months I researched the CV carb on my bike to see what I could do because I hate spending money. Took the carb off cleaned it with carb cleaner. When assembling it I was carfull and ensured no gaskets or rubber diaphrams we out of place or pinched. Reinstalled the jets. Reassembled it. Started the bike. Now it runs fine at idle and continues running even when warmed up. BUT, when I slowly turn the throttle it wants to die. Like its flooding out. If I quickly turn the throttle it revs up fine, but if I do it slowly it will sputter and sometimes die.

    With the air cleaner off the fuel looks plentiful. But the CV "pistion" (not sure on the technical part name) does not move as I slowly apply the throttle so I thought it was starving for Air. If I quickly turn the throttle the "Piston" moves up as expected so leads me to believe there is not a vacum issue.

    Sorry for the long explaination, but I wanted to fully explain the issue.
  2. kemo

    kemo R.I.P

    Lots of possibilities, could be the fuel hose is rotting and disintragating and pieces are getting through to the needle and seat causing flooding. Also try some seafoam or Marvels mystery oil in the fuel. It can work wonders.
  3. TQuentin1

    TQuentin1 Well-Known Member Staff Member Moderator

    Very likely it is the gas. Drain and clean the tank, remove the petcock and clean the screen, dump the carb float bowl, take the screws out and remove the float bowl. Clean it out from any gunk and varnish. Remove the jets and chase them with carb cleaner spray. Chase all the ports with carb cleaner spray. Carefully remove the idle air mixture needle and chase the port with carb cleaner spray. Reassemble everything.

    Refill the tank with clean gas adding some Seafoam based on volume according to the instructions.

    Fire it up and adjust the idle air mixture needle to maximum rpm then back off about 1/4 turn.

    See if that helps.


    NEWHD74FAN Experienced Member Retired Moderators

    TQ's advice is sound, likely you picked up debris that is fouling the inlet filter, or deposits and gum in the carb have settled in places that get need to be purged from the fuel system. The slow response of the CV diaphram/needle is probably due to varnish/deposits in the emulsion tube, and needle.

    While you had it apart, did the carb smell like old paint varnish, if so a through cleaning is needed. Follow that up with Gliders' tip on CV carb tuning #46 and #180 jets, and do put 2 #4 washers to lift the needle that little bit...look in the Self Help section...the Keihin Carb has plenty of development time and pretty good carb, easy tuning as you will see the rest of the recommendations. Worked great on my 2004 Sporty...the resultant carburation is crisp and you will be happy!
    Last edited: Sep 7, 2010
  5. fin_676

    fin_676 Experienced Member Staff Member Moderator Contributor

    When you snap open the throttle 2 things happen a big vacuum is created in the inlet manifold this vacuum will cause a big movement of the carb slide as the vacuum is used to suck the slide up
    at the same time the accelerator pump will will squirt neat fuel into the throat of the carb
    so snap open big movement of slide and a lot of extra fuel

    at light opening of the throttle the less vacuum so less movement of the slide but it should move up a wee bit and no extra fuel apart from the taper on the slide needle allowing a wee bit more through the main jet
    as it is bogging down on light throttle opening id suspect not enough fuel raising the slide needle a bit with a couple of washers will allow more fuel through the main jet by raising the taper on the needle
    but as the slow jet is there to proved sufficient fuel at this point a larger slow jet may be the answer to the problem fine adjustment can be done with washers raising the slide needle

  6. bigcam

    bigcam Account Removed

    dlclay you do not have that carb clean yet stop do not change anything ,take it back off and clean it proper and blow every passage and bleed with a strong amount of air pressure. if you cant do that then go some place where you can thats all thats wrong with your carb