Carby bog down in low-mid rpms? to rich??

Discussion in '2-Stroke Engines' started by linnix13, Sep 11, 2009.

  1. linnix13

    linnix13 Member

    its a small 33cc zooma engine(

    and it has been broken in, i ran it on 20:1 to break it in, it says 20:1-25:1 on the gas lid, it ran rough for the first few tanks of gas, then after 4 tanks it ran real good, it ran perfect for 2 tanks of gas and now on this chilly night it was a pain to start, it ran with very little power in the mid-lowish rpms, it would pick up and go but just as it would begin to pick up it bogs down and slows down, if i let of the gas to 3/4th full throttle it stops boging and begins to run faster and faster and once i get thru the bog rpms i can give it WOT and it will pick up and go!! why is bogging in just this rpm? it ran so good on 20:1 before and now it doesnt? i took the air filter cover off and noticed alot of unburned blue goo in the filter and leaking out of the intake, its oil not gas, straight 2 stroke oil unburned, i pulled the plug and it was mostly black exept the arc was brown but only at the tip, so i think i will clean the air filter and put in 25-1 from now on, is this likly the problem? also it has a torch bm6a plug, what would you recomend for another plug? diamondfire any good?

    oh and i have 9 litters of 20:1 left, how many leatres of straight fuel would i add to get 25:1??
    Last edited: Sep 11, 2009

  2. barebones

    barebones New Member

    you've described my probs exactly, can anyone help?
  3. motorpsycho

    motorpsycho Active Member

    sounds to me like it's too rich. but, normally in cold air, the mixture will lean out just a bit because cold air is more dense than warm air.
    or, you have an air leak somewhere because normally, you will get the bog like you describe with an air leak. you can power through the bog by playing with the throttle.
    it is normal for a 2 stroke to spit oil & gas back out through the carb and into the air filter, but it shouldn't be a lot. in my experience, "normal" means that you will see a little bit of oil/fuel on the filter, but it should not be caked or plugged up with oil.
    what could be making it spit as much as you describe? i really have no idea other than it sounds like it's running too rich (fuel/air ratio, not oil/fuel ratio)
  4. Al.Fisherman

    Al.Fisherman Active Member

    "oh and i have 9 litters of 20:1 left, how many leatres of straight fuel would i add to get 25:1??"

    I'm not a litter man, living in Alabama, but by my calculations 2 litters of fuel.

    At 20:1 9 liters (9,000cc) of fuel and 450cc of oil (what you have)
    At 25:1 11 liters (11,000cc) of fuel and 440cc of oil. (what you want)

    9,000cc (9ltr)/20cc (20:1) = 450cc.......
    11,000cc (11ltr)/25cc (25:1) = 440cc forget about the 10 cc's this time and then go with 40cc to the Ltr.
    Last edited: Dec 6, 2009