Fuel Mixture Correct, but still smoking bad and oil everywhere

Discussion in '2-Stroke Engines' started by skinnerman, Jul 25, 2014.

  1. skinnerman

    skinnerman New Member

    So Hi I'm new here. . .

    I just got my 68/80cc engine kit from bikberry.com, http://www.bikeberry.com/66-80cc-flying-horse-silver-angle-fire-bicycle-engine-kit-2-stroke.html

    Aside from mounting trouble it works great, but I'm a little worried about the gas/oil mixture.

    There is constantly a thin blue smoke coming out of the exhaust and the spark plug is filthy black, and there is oil everywhere around the head of the spark plug.

    Just like they said, I am using a ratio of 18:1. I used 5.2 oz. of oil and 93 oz. of gas. Isn't that correct?

    And for the carb I already have it on the leanest mixture possible.

    So can someone help me out? Thanks!

  2. Fabian

    Fabian Well-Known Member

    You can safely operate the engine at 25:1 from the word go. Don't give too much concern about the break-in process either.

    These engines will smoke at idle unless running 50:1 oil/fuel ratio.

    A lean """jetting""" mixture will not be good for long term reliability. The engine needs to be jetted for optimal air/fuel ratio which generally tends to be on the rich side of stoichiometric.
  3. crassius

    crassius Well-Known Member

    I wouldn't worry as long as it runs until you get enough miles on it for the rings to seat - I rarely even try to tune them until 3 or 4 hundred miles are on it.
  4. jaguar

    jaguar Well-Known Member

    How to test the filter? Take it off and blow thru it while letting it seal around your mouth.
    You shouldn't feel any additional pressure to blow thru it.
    Change the oil ratio to 25:1
    click on my signature link to find out how I leaned out my stock carb before tossing it in the trash and replacing it with a pro carb.
  5. skinnerman

    skinnerman New Member

    Here is a picture of my spark plug after I put the carb to the leanest mix and using 18:1.
    So do I need to change the air/fuel mix? And am I ok with running my 18:1 fuel/oil mix for the rest of my tank?

  6. HeadSmess

    HeadSmess Well-Known Member

    use it up, or just add the same amount of fuel as what you have to it... modern oils are far superior to the muck they seem to use in china...

    i run 50:1 with no internal issues yet... always been a lil pool of this red goop in the bottom of the crankcase when i pull em apart... ie, oil. and (until i painted over it the other day) its taken almost a year for this black streak from the exhaust join to wrap right round to the intake on one engine. flange is too thin . always warps a bit, not that that bothers me. if i keep filing it flat, it just gets thinner!

    always get some smoke on first startup too. vanishes after a minute or so.
  7. KCvale

    KCvale Motorized Bicycle Vendor

    You can try running a little colder plug.
    You don't mention where you live in your profile but if it's cold county you want a lower temp number in the spark plug size, this keeps more heat in the engine to prevent plug fouling.

    For example I am in Phoenix, AZ where triple digit heat is a daily thing in summer so I run NGK BPR7HIX or even an 8 Iridium spark plugs to dissipate all the heat I can in all the 2-strokes I build, a 6 or even 5 may better for you.

    Also when you have your plug out turn the fuel off and pedal the bike up and down the street with the clutch out to blow any excess fuel out of your crankcase, it's easy and worth it.
  8. jaguar

    jaguar Well-Known Member

    experts don't even look at the plug. they just try different jetting and see how it runs.
    there are jetting recommendations on my site to inform about symptoms of too rich and too lean