CNS adjusting help needed- weird idling

Discussion in '2 Stroke Bicycle Engines & Kits' started by mattrgray, Jul 28, 2017.

  1. mattrgray

    mattrgray New Member

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    So I've recently purchased my third cns carb, ( I love them but the clamps seem to like to break) but I cant get it to idle right. Has a number 72 jet. When I let off the throttle the idle is way up high around 3500 rpm but if I let it sit over 10 seconds it will drop down and very nicely idle at 1900-2300. If I try to tune it down while its at 3500 rpm it just dies. If I'm riding when I stop (I usually pull the clutch and ease to a stop) I have to let the clutch out and pull it back in while I'm almost stopped to slow down the engine. could you guys help me with this?
     
  2. crassius

    crassius Well-Known Member

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    certainly sounds like an air leak, but could be slide sticking
     
  3. xseler

    xseler Well-Known Member

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    I ran a CNS V3 carb for 3 years. Fought it weekly for most of that time. The easiest and best 'adjustment' I found was replacing it with a NT carb..............Easier to tune, stays tuned, and lost no top end speed.

    Best of luck with your tuning!
     
  4. mattrgray

    mattrgray New Member

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    I've had air leaks in the past but I have gasket maker on the intake sealing the carburetor, and the slide feels free, it doesn't bind or anything
     
  5. mattrgray

    mattrgray New Member

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    Yes I've found that with the NT my bike runs pretty good, but the cns gives me more low end torque and that is really helpful because I live in a hilly area.
     
  6. crassius

    crassius Well-Known Member

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    could be leak at intake gasket, or if bike has been sitting a while, could be leak at base gasket - try spraying water around there to see
     
  7. mattrgray

    mattrgray New Member

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    I will try, but i just put my NT back on and it runs pretty good just a little less power in the low end but it idles great, comes right down to 2000 and holds steady. I've noticed that the throttle response is also alot better with the NT. I might be looking into the Mikuni VM18
     
  8. xseler

    xseler Well-Known Member

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  9. mattrgray

    mattrgray New Member

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  10. crassius

    crassius Well-Known Member

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    wonder how easy to make an adjuster on bottom of float bowl as carbs had in 20s and 30s with lever for rich/lean to handle loads and hills

    seems outboards had them too for speed for travel or power to pull skiers

    guess just a tapered needle to stick up into jet would do it
     
  11. xseler

    xseler Well-Known Member

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    My issue is that I take my bike from Oklahoma to New Mexico or the Colorado mountains and it's always a crapshoot on how it's gonna run. This carb would eliminate the guess work. 1200ft to 8500ft is a big variable.......and for some reason, it never seems to like the jet that worked last time.
     
  12. mattrgray

    mattrgray New Member

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    I have an old outboard and the carburetor on it has a little thumb wheel under the bowl which moves a needle up and down below the jet, that sure would be nice on these bikes for on the fly tuning.
     
  13. crassius

    crassius Well-Known Member

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    yeah, bowl on NT is thin - have to find a way to bond something thicker to it to make threads in
     
  14. Chaz

    Chaz Active Member

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