Break In Break in: Misfiring and Runs Rough

Discussion in '2-Stroke Engines' started by mbatl, May 6, 2009.

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  1. mbatl

    mbatl Guest

    I just started the break in period on my 80cc motor, everytime it is on it misfires heavily and typically runs better on choke. When I am able to run off the choke it bogs heavily at low rpms and is more responsive at higher rpm's.

    My searches indicate its running lean because it runs better on choke, and will usually die if I move it off the choke setting.

    So far I have:
    -Tried several adjustments of idle screw
    -Sprayed starting fluid around carb. area to check for leaks-it didn't seem to have any.
    -Taken apart carb. and sprayed everything to clean it.
    -Tried different ratios of gas(from clouds of blue to clear exhaust)
    -Changed spark plug

    Regardless, it still misfires or sputters to the point the bike lurches back and forth. Does anyone have any ideas why its running so rough. Also, how fast should the fuel go down the fuel line because it tends to just sit there for awhile in the fuel line. I know its supposed to be fuel efficient, but I'm thinking the carb may not be giving enough fuel.

    Thanks for reading and responding.

  2. Junster

    Junster Member

    Use a piece of fuel line with the bowl off and blow thru it. See if it it's easy to blow thru and raise the float with your finger to see if it shuts off ok. I'd check the float level. You can bend the tab just a lil so it fills up more. Are you using an inline filter? While you have the carb apart check the jet to make sure it doesn't have anything stuck in it. To get a richer mix at lower rpm. lower the clip on the needle one notch. I'm assuming you checked for a leak where the intake attaches to the cylinder. As far as flow from the tank goes, just disconnect the fuel line from the carb and run some into a jar. It doesn't have to be huge but the flow should be steady. I replaced the plug wire with a standard auto one. It just unscrews from the CDI, they are a common source of grief.
    Last edited: May 6, 2009
  3. spad4me

    spad4me Member

    Last edited: May 7, 2009
  4. Mountainman

    Mountainman Active Member

    yes as stated above -- sounds like it's time to play with your carb

    sometimes these HT THINGS just don't run that good right out of the box

    somebody needs to be a working on that issue -- !!!

    ride that THING once up and running well
  5. mbatl

    mbatl Guest

    I looked at the links supplied, before I tried to drill out the jet I moved the needle clip one notch, which helped it run better. My last long ride it didn't jerk and misfire heavily. However, it runs really rough down low now...i'm thinking it really is the carb, which will be hard to find a drill bit that small.

    I can see the spark firing with the plug out, but it doesn't start now. I'll try to adjust the float level because bubbles come up the fuel line slowly when its off, and when I push the tickler the fuel in the line doesn't go down like usual into the carb.
    Does this mean the float is incorrectly positioned or the jet diameter is too small?
    Also, it will not cut off when its warm and the choke is put on, shouldn't it cut off? This means its running lean right?

    Update: I adjusted the brass clip that pushes down the float in the carb, I bent it up some. Now it runs but just like before at 1/4 throttle it vibrates really badly. The vibration comes at a specific throttle position not rpm, any ideas what this means?

    Thanks for reading and responding.
    Last edited by a moderator: May 8, 2009
  6. mbatl

    mbatl Guest

    I drilled out the jet and moved the needle clip back to the original position, which helped it run a little better.

    But the main problem is that it tops out much lower than it should by making a putt-putt should way before redline (I've had it at higher rpm's on a different setting). The other problem is that around 20-30% throttle it shakes very badly to the point I avoid that throttle position, what does that mean?

    The lean condition is getting better because now if I apply choke it run die if I give it gas, but should it die automatically?

    Thanks for reading and responding.