NT carb stock jet size?

Discussion in '2 Stroke Bicycle Engines & Kits' started by mattrgray, Jul 31, 2017.

  1. mattrgray

    mattrgray New Member

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    So I've got my NT on and its running good but it is fouling the plugs after 30 miles or so. Ive moved the needle down to make it run a little leaner but its not really helping. My question is what size jet comes stock with the NT, I know I want to make it leaner but where do I start.
     
  2. Greg58

    Greg58 Well-Known Member

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    Move the clip up to lean, down to richen. As you open the throttle the needle is raised out of the jet to let fuel be drawn into the engine, so the longer the needle stays in the jet the leaner the mixture. At wide open the needle has no effect, then the jet size controls the mixture. First get the jet right then lower the needle to get the setting from idle to mid range. Most stock nt carbs are rich so replacing or soldering and redrilling the jet is the only option.
     
  3. Greg58

    Greg58 Well-Known Member

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    Everyone has their opinion but I run good smokeless oil at 32/1 and have had good success, a good after market air cleaner helps engine life also.
     
  4. MotorBicycleRacing

    MotorBicycleRacing Active Member

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    66 usually works good.
     
  5. Greg58

    Greg58 Well-Known Member

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    I've always soldered and drilled my jets, its so hard to recommend what someone needs I suggest a micro drill set. I've learned like most that one engine needs a 71 while the next needs a 66 or 68.
     
  6. mattrgray

    mattrgray New Member

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    Thanks very much
     
  7. mattrgray

    mattrgray New Member

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    Jets aren't that much for a set of them so I'll just buy some for now, I haven't tried drilling and soldering jets but ill try it sometime, Thanks.
     
  8. xseler

    xseler Well-Known Member

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    Like Greg also said, oil ratio also comes into play with the jet size. I run 50:1 synthetic, and my setup is happiest with a 64 and the needle set on the second notch from the top. If I ran 40 or 32:1, the jet would usually be bigger.

    As also stated, your results may vary.
     
  9. xXNightRiderXx

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    I am running a 66 jet, with a 20:1 ratio. I am progressively working up to a 35:1 ratio. I have to have the throttle cable tightened to the point where I'm idling at 1800± rpm to keep it from dying. Once I get to the 35:1 ratio, I should be able to loosen the cable again.
     
  10. Greg58

    Greg58 Well-Known Member

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    What type of oil are you using? It sounds like you need to lean out the oil ratio before changing the jet. I start a new engine at 24/1 then as mentioned go to 32/1. I'm still running one bike that I built in August 2011 that is running that ratio.
     
  11. allen standley

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    All motors are a bit different. NT work best for me. With a brand new engine I start with the 32/1 ratio. Before the first start I'll pour a tablespoon or so of straight 2 cycle in the spark plug hole and give it a few turns. I'm @ 65ft above sea level, With a stock exhaust, clip in center position and a 66 jet size I get a good running engine slightly running rich which is great for break-in. After a couple tanks of fuel I'll lower the needle (raised the clip one position).
    If I use a modded exhaust - well that changes everything.
     
  12. crassius

    crassius Well-Known Member

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    I use the original chinese clone of the NT - the one with chinese characters on the slide tube - never had to rejet one of those for an unmodified motor.
     

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