engine revving up and down

Discussion in 'Mechanic and Repair' started by ein999, Jul 18, 2008.

  1. ein999

    ein999 LawnSite Member
    Posts: 156

    engine revving up and down but. The only way to stop it is to apply choke. what could be causing this.

    15 hp kawasaki
     
  2. The Rookie

    The Rookie LawnSite Senior Member
    Posts: 296

    water in the gas?
     
  3. ein999

    ein999 LawnSite Member
    Posts: 156

    nope no water in the gas.

    When i say stop it i mean to stop the revving or surging of the engine up and down.

    So the choke helps to stop the revving up and down.
     
  4. The Rookie

    The Rookie LawnSite Senior Member
    Posts: 296

    water inside carbureator bowl? Carbureator problem?
     
  5. AmsoilPower

    AmsoilPower LawnSite Senior Member
    Posts: 938

    You will need to clean the carb, particularly the main jet and high speed circuit. A good cleaning should take care of it. Always, always drain and clean your fuel tank also and replace fuel filter. Be sure to get a sample at the very beginning of draining if it is a gravity feed tank. This will tell you if you have water in your fuel since it will settle at the bottom. Also check for any debris (dirt, sand,leaves, plastic from inside of tank, etc.)Good luck.
     
  6. AmsoilPower

    AmsoilPower LawnSite Senior Member
    Posts: 938

    The surging stops when the choke is applied because all fuel circuits are dumping fuel into the engine. Surging starts from a restricted jet or fuel circuit. When choke is applied, fuel is pulled thru the carb in circuits (idle) that usually are not used during high speed operation making up for the restricted jet.
     
  7. Phil G

    Phil G LawnSite Senior Member
    Posts: 843

    This man's got it right. Do this and all will be good.
    Just one thing to check while the carburetter is of; the gasket between the carb and the block. Make sure it's 100%. Usually they are, but i've known them to leak.
    Now, get that carb' torn down
    atb Phil :)
     
  8. jkason

    jkason LawnSite Senior Member
    Posts: 548

    How old is this unit, and are you maintaining it regularly?

    If it's older, check to make sure that there is no play in the throttle shaft either.
    If there is, it's sucking too much air through the gap around the shaft - time fora replacement carb (or engine if the hours are really high).
     

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