Fuel Mixture 66cc cylinder on a 48 cc crankcase and crankshaft - runs too rich

Discussion in '2-Stroke Engines' started by lazylightning@mail.r, Sep 15, 2014.

  1. lazylightning@mail.r

    lazylightning@mail.r Active Member

    Hi Everyone!
    A fellow I know put a 66 cc cylinder and piston onto a 48 cc engine base. It's running way too rich. The plug needs to be cleaned all the time with massive buildup. The same carb with the same settings ran normal with the 48 cc cylinder and piston.
    Could the narrow space of the smaller 48 cc crankcase and crankshaft be actually choking off the air flow and pulling more fuel from the carb with the larger volume cylinder?


  2. crassius

    crassius Well-Known Member

    if he actually did what is claimed, widening the top of the cases to accept the larger cylinder should have narrowed the transfer port passages to about nothing

    first thing that comes to mind is "WHY?"
  3. butre

    butre Well-Known Member

    plug fouling is a result of too much oil, too cold a plug, or irregular spark.

    there would be about 3mm of transfer port left if he actually did this
  4. lazylightning@mail.r

    lazylightning@mail.r Active Member

    According to him, the cylinder fit right in without modifying the cases. I want to see it for myself.

    He's using the ngk b7hs.
  5. jaguar

    jaguar Well-Known Member

    the stud spacing for the cylinder is different (longer) for the 66cc than for the 48cc.
    I was able to put a 60cc cylinder on without modification so maybe that is what he did.