Real bad stutter/hesitation

Discussion in 'Engine, Fuel and Exhaust' started by Recon72, Mar 7, 2011.

  1. Recon72

    Recon72 Member

    Here is the situation. I just rebuilt the carb on 04 Fatboy. I followed Gliders advice on Twin Cam carb tuning and jetting. Best info I have found yet. Any the problem is this. I took the girl out for a ride the other day to warm her up so I could tune the carb. While I was riding I noticed that she would hesitate or stutter real bad around 1/8 - 1/4 throttle. If i could get the bike to power past this point she ran strong. I got back to the house and tried adjusting the a/f mixture.

    She didn't start to stumble until the screw was fully seated then when I backed it out to wear it ran steady again +1/4 i took it back out and the same thing real bad hesitation in the same throttle position. Her are the carb stats:

    jetted at 190 and 46
    needle shimmed at .050
    a/f mixture 2 1/2 turns out.
    previous owner drilled the slide to 7/64th

    Any help would be great. Thanks in advance.
  2. kemo

    kemo R.I.P

    You should be check for a vac leak at the manifold. Spray wd40 around the base of the manifold to the heads and notice any rpm changes
  3. maine-e-axe

    maine-e-axe Junior Member

    Check the vacuum line that goes to the V.O.S, it runs the vacuum advance on the timing. Unhooked or cracked hose?

    BUBBIE Well-Known Member

    I would think this Could be the Problem

    previous owner drilled the slide to 7/64th
    Slide NOT reacting properly?...

    I have Never liked the Slides drilled.. Mine, I would replace it with a stock one.


    7/64 isn't much tho
  5. Recon72

    Recon72 Member

    I will check tonight or tomorrow for any leaks at the manifold or vacuum leaks. I am thinking about putting a new stock slide in it also. I will let you guys know what I find out.
  6. Bodeen

    Bodeen Well-Known Member Staff Member Moderator Contributor

    Why the rebuild? Did it stumble before the re-build? Is it when you first crack the throttle or does it stumble if left in one spot? I'm thinking accelerator pump if it is when you first crack the throttle. Did you get the little arm back in place for the accelerator pump? Does the slide move up and down when giving it throttle? Maybe the slide diaphram is not seated properly?
    Its all about the details. Let us know. Lots of help here.

  7. Recon72

    Recon72 Member

    I rebuilt it because the previous owner left the bike sitting with the same gas for over a year. I just figured I would rebuild it since I had it off any way. I was looking at it and it had a lot of gunk in the float bowl and I noticed the guy had a 50 slow jet in it. On the ride home she did not stumble but she was a dog. I followed Gliders info hoping to bring some pull back to her. I will double check the accelerator pump.

    It is stumbling the whole time it is anywhere between 1/8 to 1/4 throttle. No matter what gear I am in. Some times it is so bad it will die out.
  8. glider

    glider Veteran Member

    The stumble could be a result of a problem with the slide as in the diaphragm not seated properly (aside from the redrilling) or leaking/holed, top not seated right causing a slower than normal rise. The 50 is much too big and the 46 is where you should be. See if the accelerator pump is giving you a healthy squirt when you open the throttle.
  9. Recon72

    Recon72 Member

    Thanks. I am going to check this stuff out tonight or first thing in the am. I will let you guys know what I find.
  10. NEWHD74FAN

    NEWHD74FAN Experienced Member Retired Moderators

    One other thing, when dealing with carburetor, there are a lot of parts, easy to reassemble them improperly if you do not pay attention how everything disassembles...especially the CV slide needle parts (spring tension can have you on your hands and knees looking for parts)...disassemble methodically...and note any "extra" parts that should not be left...:s