motor runs for a block then wont accelerate

Discussion in '2-Stroke Engines' started by j2thevvizo, Dec 4, 2009.

  1. j2thevvizo

    j2thevvizo New Member

    my bike is giving me problems. its struggles to start up sometimes but eventualy it starts and i ride for a block or two and the all of the sudden it wont accelerate any more. the motor is still on and it just doesnt go when i twist the throttle. i stop and try to start it again and it struggles to start but then eventually it fires up and rides for a few blocks and doest it again. ive never had a problem with the engine until now. its always been fine. i thought it was the throttle but the cable seems to be pulling the valve side in the caburator properly. im thinking that it may be a spark plug problem or too much fuel is getting into the combustion chamber and its flooding. any ideas would help. thanks
     

  2. Slamazon

    Slamazon New Member

    it could be running too lean and starving for gas. i find this problem alot with my nitro powered R/C cars, loss of power and run hot in a lean condition. same with my gas trimmer. a simple carb adjustment could make all the difference in how it runs.
     
  3. j2thevvizo

    j2thevvizo New Member

    ok ill try. that means that i have take out the carb pin and put the little washer on a different notch. which way do i move the washer to make it less lean? thanks for the reply
     
  4. AussieSteve

    AussieSteve Active Member

    If it was previously OK and you haven't changed anything, then you shouldn't need to change the slide needle setting.
    You've cleaned or swapped the plug? If not, that's first.
    It sounds like it might possibly be starving for fuel, from fuel not flowing into the float bowl quickly enough. It wouldn't hurt to disconnect the fuel line at the carby then turn the fuel petcock on and see if you're getting a decent fuel flow. The fuel filter may be blocked.
    If that's OK, pull the carby off and clean it, ensuring nothing is blocked.
    What colour is the plug? If it's starving for fuel the mix will be lean so the plug will be dry and light coloured. If it's rich or flooding, the plug will be black. If the mixture is OK, the plug will be a tan colour.
    Let us know how you go.

    ... Steve
     
    Last edited: Dec 4, 2009
  5. motorpsycho

    motorpsycho Active Member

    I was also going to suggest replacing the fuel filter and make sure the air filter is not plugged up. a plugged air filter will make it run too rich and bog.
    No carb adjustments should be needed if it has always ran good and he didn't change anything on the motor.
    but, it could be that the jet needle c-clip was set to make the motor run on the leaner side and ran fine in warm weather. not sure where he is located, but if the carb is set on the lean side, and he is now running in colder weather, it could be too lean now. colder air will make it run leaner...just a thought.
    to richen the carb, move the jet needle c-clip down from the top(which raises the jet needle allowing more fuel to flow through the main jet). to lean it, move the c-clip up (which lowers the jet needle into the jet, allowing less fuel to flow through the main jet). the more the jet needle is inside the jet, the leaner it will be. by moving the c-clip up or down, you raise or lower the jet needle.
     
    Last edited: Dec 5, 2009
  6. AussieSteve

    AussieSteve Active Member

    Checking the air filter is a good suggestion.
    ... Steve
     
  7. Al.Fisherman

    Al.Fisherman Active Member

    After all of above (I agree with both AussieSteve, and motorpsycho) check your exhaust...strange things happen.
     
  8. gemballa

    gemballa New Member

    I recently installed my first 80cc chinese kit on a mountain bike, I had the same problem, the engine started, then after few meters would stop....

    Then I realized that I installed the carburator on the wrong side (up-side)

    THe black plastic tubes for air intake should be downside, than worked wonders

    SO maybe your problem is the carburator, or something related with air-intake
     
  9. AussieSteve

    AussieSteve Active Member

    You actually got it running with the carb upside-down for long enough to do a few metres? That's got to be a first. Well done!
    Maybe that's j2thevvizo's problem.

    ... Steve
     
    Last edited: Dec 7, 2009
  10. gemballa

    gemballa New Member

    Like 6 meters hehe, Im a newbie, giveme a break lol
     
  11. AussieSteve

    AussieSteve Active Member

    Sorry gemballa, just having a bit of fun and don't worry, we've all made our share of silly mistakes.
    Just the same, I'm surprised that you got it started.
    ... Steve
     
  12. motorpsycho

    motorpsycho Active Member

    i don't see how the motor even ran with the carb on upside down. there is no possibly way for it to run, plus the throttle cable would have been coming out on the bottom, kinked & more than likely not functional. the fuel line would have been on the opposite side, so he would have had a mile long fuel line (more than likely with kinks) from the tank to the carb. PLUS, when he opened the fuel tank petcock the carb would have just leaked fuel out all over the place, and there is no way that the float bowl would have ever filled up. if the float bowl did fill up with fuel, all of the fuel would have just drained out of the main jet by gravity. the fuel woudl have either flooded the cylinder, or just ran out the back of the carb. I don't see how the float bowl would have ever gotten fuel, or how the engine would ever run.
    maybe he just put the air filter on upside down?
     
  13. Al.Fisherman

    Al.Fisherman Active Member

    My first thought was, how in the world can one put a carburetor on upside down, then my immediate thoughts were the same as yours. The only thing I can think of is that the fuel wasn't on till he tried to start it then maybe, MAYBE, enough fuel got into the cylinder and fired. Strange things can and do happen.
     
  14. Al.Fisherman

    Al.Fisherman Active Member

    Are you telling us that you actually mounted the carburetor on the cylinder such as in one of the two pictures below?
     

    Attached Files:

  15. motorpsycho

    motorpsycho Active Member

    the carb could techically be mounted to the intake anyway you want to mount it because there is no keyway, flat or notch in the intake tube to orient the carb. the correct way.
    sure, it could be mounted upside down, but i highly doubt that the engine would run.
    BUT, maybe... in a million to 1 chance that the conditions were right and it actually ran would be amazing.
     
  16. Mike Hunt

    Mike Hunt Member

    my guess is that op probably meant that it was sideways rather than upside down. depending on which side was up its quite possible that it might have fired a couple times.
     
  17. AussieSteve

    AussieSteve Active Member

    When I think about the possibilities, Al's pics or Mike Hunt's suggestion, they would all allow some fuel/air to be sucked into the intake, but all would have fuel p i s s i n g out of the carb. I wouldn't be trying to start it, but it is possible that it would run for a couple of seconds.
    Anyone care to try?
    (Not me)

    ... Steve
     
  18. j2thevvizo

    j2thevvizo New Member

    ok it rained for a day or two so i just got trying make my bike work. first thanks for all you replys. all your ideas about the not getting enough fuel to the combustion chamber were correct but not for the reason i thought was going to be. when i went to check my fuel filter and fuel line for some reason on loosed my gas cap and i notice the gas in the tube start rushing down into the carb after i has taken the cap off. i tried the riding the bike with cap on but loosened and it worked fine. i tried tightening the cap and the bike stalled out. it turns out that my gas cap creates a seal that prevents the gas from flowing through the filter. so now i have a new problem. i have to ride with gas cap loosened ad risk splashing fuel all over me. has anyone else had this problem. is the something i dont now.
     
  19. AussieSteve

    AussieSteve Active Member

    Wow. You know, after I posted my suggestions the other day, 'vapour lock' crossed my mind, but I discounted it because virtually all of these caps leak.
    It does raise an important issue.
    I wonder how many others are experiencing this to a degree? Even though most caps weep a little, it's not necessarily enough to compensate for the potential vacuum if the cap can't breath.
    About all that I can suggest is a tiny, (~0.5mm - 1mm), hole in the cap. Or try another cap. I've got two and one seals really well, so I might have the same problem. (That cap is on my 3L tank, not fitted yet.)
    On many dirt bikes, a thin hose runs from the cap to the handlebars to allow the tank to breath without weeping through the breather hole.

    ... Steve
     
    Last edited: Dec 9, 2009
  20. gemballa

    gemballa New Member

    Yeah! Like the right picture, the motor was brand new, so it had clean air on the system I guess, and ran for about 2 seconds

    Its true, belive me if you can!
     
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