How to Tune Carter model N carb

Discussion in 'Whizzer Motorized Bicycles' started by MaxGlide, Oct 6, 2009.

  1. MaxGlide

    MaxGlide Member

    OK, I've searched online and found how to basically tune this carburetor but I just need clarification on a few things.

    As a starter I have,
    • cleaned the gas tank
    • taken the carb apart, cleaned it in carb cleaner and set the fuel float height.
    • installed a new air filter
    • put in fresh gas, flushed the system with new gas then hooked up fuel line.

    I set the jets as per manual but the instructions seem to only be for carbs with one adjusting jet. My carb has both (see pic) the "Low speed jet" adjustment (#11) and the "Idle adjusting screw" (#12). The manual tells me what to do with the idle screw but not the low speed screw....

    ANYWAY... here is what I am experiencing.
    • engine starts pretty good
    • idles ok but rpms go up and down as it sits there.
    • engine is burning oil (blue smoke out tail pipe)
    • engine bogs down when I start out so I have to help it with the pedals.
    • RPMs go up and down as I ride along.

    So I would greatly appreciate it if someone could help out with
    1. The intial settings for both the idle and low speed screws.
    2. Which one to use to make mix leaner (the idle screw has an arrow that says "leaner" on it so I'm guessing that is the one)
    3. How big or small the adjustments should be.
    4. If I am setting the mix leaner, how quickly I would see a cleaner fuel burn

    Thanks to all in advance.


    Attached Files:

  2. MaxGlide

    MaxGlide Member

    Thank you Quenton

    I Pm'd Quenton and of course he had the answer.

    Thanks so much. I'll let you know how it turns out.

    The only advice I am afraid of is to run it wide open to tune it under load. I don't know if I trust myself or he 1945 Elgin at full speed!

  3. Nolan

    Nolan Member

    yeah I was wondering about adjustments today, my bike has been fouling spark plugs and I have been adjusting the fuel/air mixture and it hasn't improved.
  4. Quenton Guenther

    Quenton Guenther Motored Bikes Sponsor

    Hi MaxGlide.
    If you don't have any luck you can send the carburetor to me and I will test and adjust it on one of my vintage Whizzers and send it back ready to work correctly.

    Which motor are you using, "J", or 300 series?

    Have fun,
  5. kwaskow

    kwaskow New Member

    Possible to post the adjustments for both low speed and idle screws?
  6. MaxGlide

    MaxGlide Member

    Stand by.... I will find the sheet that Quenton sent me on how to adjust it and pass that on...

  7. kwaskow

    kwaskow New Member

    Thanks!! Looking forward to it