Problem at low rpms

Discussion in '2-Stroke Engines' started by DanielMaia, Mar 28, 2011.

  1. DanielMaia

    DanielMaia Member

    Hi there guys,

    Installed a new Dellorto SHA16.16, rejetted to #62 (live 80 meters above sea level), new expansion chamber, and have some problems.

    If the engine its cold, it starts fine, 4 strokes at high rpms..but its normal.

    With engine hot, low rpms it boogs...lost of power..i need to pedal a little (up hill), but when i reach 6000RPM, it starts to rev to the infinite, pulls me from 40 to 54km/h like a rocket, pulls really very fast.

    Idling its very inconstant..

    Intake air leak? Why with engine cold it runs fine?


  2. adb140275

    adb140275 Member

    if its a 66cc, 62 sounds way way too small. stock NTs (14mm) run best on a 68 (stock being 70). When i get my 15.15, im going to try a 70 first.

    keep in mind... bigger carb=more air, more air requires more fuel
  3. DanielMaia

    DanielMaia Member

    Hmm, ok, lets suppose the main jet is way too it normal to revv like crazy at high rpms?
  4. adb140275

    adb140275 Member

    if a SHA had more than one jet, it would sound like tuning. inconsistent idling sounds like an air leak... dellortos never leak on the intake because they have the plastic shim. check your intake gasket where the intake bolts to the cylinder.
  5. DanielMaia

    DanielMaia Member

    nop, intake its perfect, cause i put th NT stock carb (modded to 15mm), and pulls me up hill at 31mph, idle its really perfect.

    Maybe its main jet?

    Other thing...its really hard to kill the engine by closing the "air" ...its a symptom?
  6. adb140275

    adb140275 Member

    yeah it should be too rich when its cold and lean out when its hot. try a bigger main jet. 62 just seems way too small. take the jet out of your NT and put it into your dellorto, they are cross compatible
  7. DanielMaia

    DanielMaia Member

    yes, i bought a set of jets. I will put a 70 jet on it!