03 Sportster carb pop

Discussion in 'Engine, Fuel and Exhaust' started by nascar7613, Jun 15, 2009.

  1. nascar7613

    nascar7613 Active Member

    We just aquired an 03 Sportster with 90 miles on it. Upon disassembling the carb, the pilot and main jets were restricted. We could not unclog the 42 pilot jet. We had a 45 here, so we installed it. The bike runs fine under medium to heavy acceleration. It seems to struggle a bit when taking off from a dead stop. It also seems to cut out at steady speed and low rpm, say at 45 mph in 4th gear. The bike has stock exhaust but has an air box from a 07 Sportster, which appears to have more air inlets then the original air cleaner. Read the self help but couldn"t find this particular problem. Any advise would be appreciated.
  2. glider

    glider Veteran Member

    The 45/46 should be fine for the low jet. Your problem with dying could be a restriction in the main jet area or the diaphragm may have a defect in it.
    You didn't mention what size the main jet was. You could also use 2 - #4 washers under the needle to lift it up and give you an earlier fuel delivery which would come in at cruising speeds.

    Sportster CV Carb Rejetting - Harley Davidson Community

    Quick and easy way of testing the main jet size.

    Run the bike through the gears into third gear and run third up to 60-70 MPH full throttle, then chop the throttle about 1/8 to 1/4 back and see if the bike either surges ahead or stumbles then recovers.

    If it surges ahead, your jetting is lean
    If it stumbles and recovers , your jetting is rich
    If it makes no difference, you're pretty close.

    You'll also find some info that pertains to your carb in this post too...

    *Twin Cam CV Carb Rejet Suggestions - Harley Davidson Community
  3. Old legend

    Old legend Member

    Something else to check. If the bike has been sitting with gas in the tank, you might want to take the tank off, drain all of the old gas out, clean the tank out and the petcock screen, and then put it back on with new gas. Also run a few tanks of gas with STP (or whatever brand you choose) carb cleaner in it.
    When my son gave me my 883, it had been sitting since 2003 with a half tank of gas and it gummed up the inside of the tank and had solid something in the carb, especially the idle jet, it was solid. I took it apart and sprayed it heavily with carb cleaner and used an old toothbrush to clean it. Now it runs like a charm.