running her hot

Discussion in '2-Stroke Engines' started by coyote888, May 8, 2015.

  1. coyote888

    coyote888 Member

    i have a 49cc that runs around 300F upper cylinder temp and 290s head temp cruising. people say this is way too hot but it seems like this is where the engine wants to run. i have adjusted the carb to run as rich as possible, plugged all potential carb leaks and yet it still runs no differently than when it was running lean. its a relatively new engine so could this be a factor? any advice to drop the temp a little? im only about 650 feet above sea level. give or take. ambient temp is 80.

  2. MotorBicycleRacing

    MotorBicycleRacing Well-Known Member

    That is not too hot.

    A Fred head with a lot more mass and larger fins will cool better,
    but if you aren't full throttle racing you don't need it.

    Adjust your carb to run neither rich or lean.
  3. coyote888

    coyote888 Member

    I took the temp again After Some harder riding and this time it was 350. Ok now it's getting scary
  4. butre

    butre Well-Known Member

    don't worry about it unless it hits 400. That gives you about 100 degrees before imminent engine failure. if it does hit 400 and getting a spark plug a heat range colder doesn't help then you need an aftermarket head with more surface area such as a fred head
    coyote888 likes this.
  5. jaguar

    jaguar Well-Known Member

    put a colder plug in and clean off the head fins if they are dirty.
    also consider buying an aftermarket CDI which lowers temps by having the spark not so excessively advanced as the stock one is
  6. coyote888

    coyote888 Member

    I can't seem to find a head for the 49/48 that are reputable. I don't think CR machine makes a 48 cc head. Also I'm not sure if the aftermarket CDI will work with the 48 since most are designed for the 66
  7. jaguar

    jaguar Well-Known Member

    the Jaguar CDI works equally on both engine sizes.
    I lived on the coast of Equador where it was plenty hot and with the Jaguar CDI and higher compression (which makes engines run hotter) I never needed an aftermarket head.
    At 450 degrees is where the aluminum loses too much tensile strength.
    The problem with aftermarket heads is that they cause too much compression (>135) which is hard on bearings and causes cylinder plating to flake off.
    coyote888 likes this.
  8. Slogger

    Slogger Member

    disregard, Jag already said it
    (Happens to me all the time!)