Jet sizes

Discussion in '2-Stroke Engines' started by andynogo, Oct 22, 2009.

  1. andynogo

    andynogo New Member

    I've been reading a few threads recently where people are talking about 1mm jet sizes and bigger (up to 1.5mm)

    I've got a '80' (66cc) kit where I had to make my main jet smaller to get the right mixture. I'm currently running at about .48mm which is perfect.

    I've got a proper airfilter (which is actually more restrictive than the swiss cheese standard bit of foam), expansion chamber exhaust, smoothed exhaust port and not much else. The bike still goes well, cruising at 40km/h no problems.

    Is my motor unusual in that it needs such a small jet or are some of the others just gas guzzlers?

  2. Pablo

    Pablo Motored Bikes Sponsor

    That does seem tiny - watch out.

    I run a .65 mm jet.

    1.5mm seems huge. My engine would be choking on fuel.
  3. andynogo

    andynogo New Member

    Thanks Pablo- with a .5mm jet it four strokes constantly and leaves a very black plug.

    I'm actually thinking of putting in an adjustable air jet to fine tune the mix- probably completely unneccessary, like most things I do to this bike! I guess I could also look around for a proper carby off a scooter or similar, but that's probably the easy way to go! :thinking:
  4. EnFlaMEd

    EnFlaMEd Member

    I'm running the 1.5mm jet and I can't explain why really. All I know is that after I swapped my stock airbox for a velocity stack and ufo filter my lean problems started. I tried .8mm, 1mm, 1.2mm and now the 1.5mm which seems perfect. At one point I even re soldered and went back to .8mm because I was convinced I had gone too big. I did that and the bike barely ran if it was given any stick. Changed back to the 1.5mm and once again shes a beast.
  5. andynogo

    andynogo New Member

    Yes, I guess no two engines are the same, hey! Whatever works, works. I remember about 150 years ago when I was 16, I had a 50cc bike which I put a 65cc big bore kit in, decent exhaust and air filter, and that needed a 1mm jet (after being told it need a .75) and the guys at the bike shop disbelieving me!

    That bike used to do 70mph flat out and was a road trail style! (Suzuki TS50X)
  6. Al.Fisherman

    Al.Fisherman Active Member

    Paul...what is the factory jet size?
  7. Pablo

    Pablo Motored Bikes Sponsor

    0.70 mm
  8. DanielMaia

    DanielMaia Member

    Hey guys,

    Sorry for my noob question, but the jet you're talking about, is the jet the fuel line is pluggled/connected?

    Or the mainjet that connects the gigleur?

    thanks in advance
  9. Pablo

    Pablo Motored Bikes Sponsor

    Neither. It the jet that is actually in the fuel float bowl. Visible when you remove the bowl.
  10. DanielMaia

    DanielMaia Member

    Here in Portugal we call the main jet gigleurs :p

    I put on mine 0.75mm, but seems that's too much :\
  11. andynogo

    andynogo New Member

    Well I've been checking mine and with a .48mm jet, the plug is just off black and runs very well. Did just over 60km/h (61.2 :grin5:) yesterday for a quick blast but she was getting a bit buzzy!