Engine running at half throttle,whats up????

Discussion in 'Motorized Bicycle General Discussion' started by fall_down_stand_up, Oct 15, 2009.

  1. fall_down_stand_up

    fall_down_stand_up New Member

    Joined:
    Apr 26, 2009
    Messages:
    555
    Likes Received:
    0
    When I pull the clutch in and rev it up it seems to rev up slower than normal and does not rev up all the way....It acts like it is only getting half throttle....I took the slide out on the carb and when I twist the throttle the slide goes all the way to the top so I know that is not the problem....Could it be weak CDI or magneto?Could it be the spark gap?The engine runs smooth as silk and at full throttle it tools along at 21 mph....Even when I go down hills it only gets upto 24mph becouse the engine is not getting full throttle for some reason....Any help would be appreciated....
    John-John
     
  2. BarelyAWake

    BarelyAWake New Member

    Joined:
    Jul 21, 2009
    Messages:
    7,209
    Likes Received:
    5
    erm... the dreaded leaks perhaps? Carb/manifold would be likely...

    That's what I would start lookin' for anyway :) Do you have idle problems?
     
  3. fall_down_stand_up

    fall_down_stand_up New Member

    Joined:
    Apr 26, 2009
    Messages:
    555
    Likes Received:
    0
    It idles perfect and runs smoothly,the spark plug is running rich and I cant choke it at all or it will die so I dought it is a air leak....The engine has 80 miles on it and im running 50:1 synthetic blend 2 stroke oil....I changed the carb out with a new one I had laying around and still the same problem....It is not 4 stroking,the idle does not go up and down it just runs smooth but wont rev up all the way....
    John-John
     
  4. fall_down_stand_up

    fall_down_stand_up New Member

    Joined:
    Apr 26, 2009
    Messages:
    555
    Likes Received:
    0
    Someone please respond to this post with some ideas of what it could be....
    Thanks
    John-John
     
  5. george_n_texas

    george_n_texas New Member

    Joined:
    Sep 4, 2009
    Messages:
    981
    Likes Received:
    3
    Mine does close to the same thing...then I start peddling real hard for about 30 yards and it kicks in...I think mine is a weak magneto or wiring.
     
  6. bandito

    bandito New Member

    Joined:
    May 22, 2009
    Messages:
    783
    Likes Received:
    0
    Fall down there is a thread going on with nearly the same symptoms and it was the linkage in the carb not working properly. Bikeguyjoe I think was the author and found the cure. I could be wrong but its a maybe. These 2 strokers have carbs Im not familiar with like japanese carbs from the threads I read.
     
  7. bandito

    bandito New Member

    Joined:
    May 22, 2009
    Messages:
    783
    Likes Received:
    0
    I tried finding it and it would take me days, I just read it in the last 2 days I know. The problem was with the cable housing not fitting properly into the housing on the carb or somthing and it wasnt letting the linkage move full travel in the carb.......maybe?
     
  8. BarelyAWake

    BarelyAWake New Member

    Joined:
    Jul 21, 2009
    Messages:
    7,209
    Likes Received:
    5
    Yeah bandito I remember that - it was excessive free play in the throttle cable and using the adjuster on the top ot the carb to compensate...

    Couldn't be that easy could it?
     
  9. fall_down_stand_up

    fall_down_stand_up New Member

    Joined:
    Apr 26, 2009
    Messages:
    555
    Likes Received:
    0
    Thanks for the responses....I took the slide out of the carb when I first had the problem and when I twist the throttle it goes all the way to the top....I Will take an extra throttle cable I have laying around and try it and see it it changes....If that doesnt work I will change the carb to a third one and see it that helps....
    John-John
     
  10. Venice Motor Bikes

    Venice Motor Bikes Custom Builder / Dealer/Los Angeles

    Joined:
    Mar 20, 2008
    Messages:
    6,213
    Likes Received:
    24
    Maybe the exaust pipe is too restrictive?
     
  11. fall_down_stand_up

    fall_down_stand_up New Member

    Joined:
    Apr 26, 2009
    Messages:
    555
    Likes Received:
    0
    I will check that out as well this morning,pull it off and see if its got a good clean shot....
    Thanks again everyone
    John-John
     
  12. bandito

    bandito New Member

    Joined:
    May 22, 2009
    Messages:
    783
    Likes Received:
    0
    Restriction in the flow of fuel is my guess, in the carb or tank or fuel line. Cant be a timing issue and from the symptoms I wouldnt think its electrical. If the gas cap isnt venting properly?
     
  13. fall_down_stand_up

    fall_down_stand_up New Member

    Joined:
    Apr 26, 2009
    Messages:
    555
    Likes Received:
    0
    I put my own little set up on the tank with a super flow shut off valve(did away with the factory junk valve),I drilled a pencil led size hole in my gas cap before I every started the motor for the first time(venting good)....I was thinking gas flow problems as well,but when I pull the fuel line loose from the carb the flow of fuel coming out is excellent....Im stumped....
    John-John
     
    #13 fall_down_stand_up, Oct 16, 2009
    Last edited: Oct 16, 2009
  14. Sydneysider

    Sydneysider New Member

    Joined:
    Mar 20, 2009
    Messages:
    189
    Likes Received:
    0
    From experience I can say a blocked exhaust will most likely cause that half throttle issue, judging by the built up carbon on the plug. If it was a lighter tan or whitish color, then the thing to look for would be air leaks..
     

Share This Page