Finally Solved, First Time Ever Saw This

Discussion in 'Trials' started by PMK, Jun 11, 2018.

  1. PMK

    PMK Been here awhile

    Joined:
    Jun 29, 2009
    Oddometer:
    213
    Location:
    SoFlo, USA
    Some of you know I have and ride a 2005 Scorpa SY250r.

    Recently it acted up.

    Bike would fire up fine, idle, rev, and do the typical things it should do. However, it was not quite as crisp as it has been in the past.

    The odd thing being, it would die rolling out of the garage, or down the slight incline of tne driveway.

    Even tested it and rode the flat sidewalk, again, would idle, rev, and accelerate, but seemed a bit rich. While riding, it would cut out as you slowed down.

    Initially, the carb float bowl was removed, jets pulled, and cleaned. Problem remained.

    For grins, while idling, I raised the front tire, lifting it by hand. The bike continued to run. Next, raised the rear tire, again, lifting it by hand. Immediately, the bike died.

    Pulled the carb again, opened the float bowl, visually inspected with a magnifier, all the jets. No blockage noted. Did not believe it was jets anyway after the raise the wheel test.

    Obviously, it must be related to the float or float height.

    With float removed, placed it into a cup of premix. No issues, floated level and fine. Next, verified the float height was accurate and correct, it was.

    Knowing it was not electrical and was not typical dirty carb, nothing made sense, and why does it die with the rear wheel raised.

    The one item not removed during carb cleaning was the choke plunger. Not expecting to find any issues there, but I went ahead and removed it.

    As it turned out, the rubber disc, on the end of tne choke plunger had become unseated and was sitting in the choke circuit sideways. When the choke was utilized, it unblocked the opening and the choke functioned as it should. When the choke was closed, the rubber disc would randomly cover portions or entirely the choke port in the carb.

    Reinserted the rubber disc into the choke plunger as it should be. Installed the carb, and the issue is resolved.

    I am sure some here have seen this many times, myself, in all my years working on motorcycle carbs, this was a first.

    Maybe, this will help someone else at some point.
    #1
    Ccino, laser17, alpineboard and 6 others like this.
  2. Norman Foley

    Norman Foley Devotee of the Husqvarna

    Joined:
    Mar 20, 2004
    Oddometer:
    1,944
    Location:
    New York... The Finger Lakes
    This happened to a friend’s TY350.
    #2
  3. PMK

    PMK Been here awhile

    Joined:
    Jun 29, 2009
    Oddometer:
    213
    Location:
    SoFlo, USA
    Probably the same or similar TK brand carb.
    #3
  4. motobene

    motobene Motoing for 46 years

    Joined:
    Mar 9, 2013
    Oddometer:
    5,074
    Location:
    Wichita Mountains SW Oklahoma
    Very clear description of problem and solution!

    Never had that happen, but now I know what else to check, thanks.
    #4
    Ccino likes this.
  5. NVTS

    NVTS Are you ennen oh eff tee

    Joined:
    May 18, 2006
    Oddometer:
    1,098
    Location:
    Big Lick Virginia
    Exact thing haunted me with my 01 Scorpa. Two mechanics couldn't figure it out either. I bought a whole new carb from Tryalsshop and the problem went away. Thanks for your diligence.
    NVTS
    #5