motor not running so well

Discussion in '2-Stroke Engines' started by akkm, Sep 12, 2009.

  1. akkm

    akkm New Member


    my motor ran great when I first got it, it probably has a couple hundred miles on it, it doesn't run so well any more, I changed the plug and I drilled out a bigger hole in the intake to lean it, it just doesn't run to well any more. also when the motor does start to wrap out (higher rpms) it seems to have high vibration, not smooth running, any ideas? its the 80cc. I'm thinking about stepping down to the 49 or 66 cc so I can go faster, I want to buy the best motor on the market, I saw the angle plug motors, any suggestions on what and where I can buy a new motor? and what mods are the best, carb, pipe, etc...

  2. Mountainman

    Mountainman Active Member

    you drilled a bigger hole you say ??
    was that when it started acting up ??

    ride that thing
  3. arceeguy

    arceeguy Active Member

    The 66cc and 80cc engines have the same displacement. For marketing purposes some sellers post total combustion chamber volume vs. swept volume, which is the traditional method.

    What did you drill out? Any change in the exhaust or intake will require tweeking of the carburetor mixture. More air without the addition of more fuel can lead to an overly lean mixture, poor performance, and possible engine damage.
  4. akkm

    akkm New Member

    I haven't touched the exhaust, we drilled a hole in it right after I got it to lean it out so I could keep up with some friends, I did check the plug and it was fine, not too lean. after that point it ran well for at least a 150 miles so I'm sure the first hole was ok. the only variable is that it has sat for about a month. last night after posting this I changed the fuel and modified the hole in the intake and changed the plug, it ran better, except for the vibration, got back checked the plug and it was way too lean for my comfort. then I started changing things, so I am at square one now. I drilled out that hole and put a small brass valve so I can meter the extra air going through the intake. along with that I ran a tube from the valve into the intake so it pulls filtered air. I'm ready to just buy a new motor, what's the best quality one out there, any links would be helpful. -thanks
  5. biken stins

    biken stins Member

    [QUOTE I haven't touched the exhaust, we drilled a hole in it right after I got it to lean it out so I could keep up with some friends,

    Maybe you did not brake it in right ?
    Were you able to keep up with them ?
  6. little bird

    little bird New Member

    tighten engine mounts to fix vibration . this is always to cause of it , loose chain also contributes
  7. little bird

    little bird New Member

    also you will be running too lean if you have made a hole in the inlet.check 4 water in carb
  8. little bird

    little bird New Member

    after 2 years of trying to make my bikes fastr (port jobs, cut pistons,rejetting ,pipes,etc), i discovered smaller rear sprockets . no more blown motors .the bike does 70km/ph cruises at 50 effortlessly .and the moded bikes are left behind .i do have to pedal a little to get going but its been 100% reliable and is totally stock .gt5 motors rule