Carby NT Speed carb problem

Discussion in '2-Stroke Engines' started by P3_Takuto, Jun 23, 2015.

  1. P3_Takuto

    P3_Takuto New Member

    So I upgraded from the stock NT carb to the Speed Gen2 carb since the stock carb started bogging and 4-stroking way too much and couldn't get it to run properly anymore so I bought the NT Speed Gen 2 carb, but this has a different problem. As it starts all is normal, it takes a little warm up to get it going to the high rpm powerband but here is where the issues start, after some riding at a mid-high rpm range for a minuet I came to a stop and the engine was revving way higher than my idle is set too as well as it us much hotter than it normally is. then it cuts out when I try to set off. i was first thinking there is an air leak somewhere in the carb. I've checked any openings I could besides opening the carb since i can't tell if the type of gasket will hold again after taking it apart since many develop leaks after being opened and closed again. So I can't tell if this is fuel delivery or an air leak or maybe both? I'm stumped here. Any help is greatly appreciated!
     
    Last edited: Jun 23, 2015

  2. crassius

    crassius Well-Known Member

    you may be looking in the wrong place - I have never seen an NT carb change its behavior unless it was full of debris or broken

    my thought is that your engine has changed behavior, so no carb will fix that
     
  3. Slogger

    Slogger Member

    Those are symptoms of an air leak. Running hot, revving at idle on its own, no power.. Re torque the cylinder head and I'd check the carb to manifold joint and manifold to cylinder for a loose clamp, loose nuts or just a bad seal. Sometimes you have to use emory cloth and a flat surface to flatten and smooth the manifold's mating surface.
    Then there are the seals and case gaskets. Those are less likely to be the trouble, I think.
    Good luck with it.
     
  4. P3_Takuto

    P3_Takuto New Member

    That's what I thought but I found the main source of the issue. On the NT Speed Gen 2 Carbs it comes with a white fuel shutoff valve which I took apart and discovered it has almost no clearance for fuel to pass through when opened. I removed the valve switch and replaced it with a rubber strip to seal the hollow casing and it runs much better now, I knew it couldn't be an air leak since I checked almost all possible places air could leak from. I was thinking that by the way it reacted anf the revving pattern after riding it was starving for fuel and had burned what it could before cutting out. All that is needed is to get rid of the white valve and seal up the casing and boom problem solved! Hope this helps anyone with similar issues with the NT Speed Gen 2 Carb
     
  5. crassius

    crassius Well-Known Member

    not sure how that valve made the original stock NT carb screw up
     
  6. BWB

    BWB New Member

    I'm having a similar problem with my speed carb. After about 10 minutes of riding when I pull in the clutch The RPM goes crazy high. I tried backing off the idle screw until it's practically falling out. Just makes it run like cr** . If I briefly pop the clutch a bit It will go back to a normal idle usually. Then it returns to crazy again the next time I come to a stop. Also it bogs out about every time I hit a bump especially at higher RPMs. Did not find any debris inside the carb or air leaks at the intake. My speed carb did not come with a shut off valve. Any ideas? Brian
     
  7. crassius

    crassius Well-Known Member

    over revving is usually a lean condition - lack of fuel or air leak
     
  8. BWB

    BWB New Member

    Why does it only happen after 15min of riding?
     
  9. BWB

    BWB New Member

    I put a new K & N style air cleaner with a velocity stack on it and that seems to have eliminated to bogging but not the crazy idle condition.
     
  10. crassius

    crassius Well-Known Member

    maybe some metal piece has a crack that only leaks air when the heat expands it ???

    did you spray it with water or something to find it?
     
  11. canalcat

    canalcat Member

    My carb is similar with a white shut off valve / took apart and found one of the two holes closed with debris!!!! Wow I hope this solves my Sputtering prob!!!!!
     
  12. BWB

    BWB New Member

    Not sure about spraying with water. Could you please elaborate?
     
  13. crassius

    crassius Well-Known Member

    if you use a spray bottle to spray water at the parts of the intake manifold where it meets cylinder and carb, you'll hear the motor slow down when water gets into the leaking spot (some folks like to spray fuel or carb cleaner or other things, but I think water is better)
     
  14. SeanPatrick

    SeanPatrick Member

    Why do you think water is better? I've never heard of doing it that way. I know that certain solvents and ether can "wash" the oil from a two strokes cylinder but I wouldn't think it'd be a problem when using it to check for vacuum leaks. You've got me curious now crassius.
     
  15. crassius

    crassius Well-Known Member

    'cause if your wiring is old and you spray anything flammable you might light your pants on fire - water works as well and never does that
     
  16. BWB

    BWB New Member

    Thanks crassius I will give that a try as soon as I can. I went on a long run today with some big hills and the hills won. My head bolts loosened up and the head gasket blew. I must have had a premonition cause I randomly ordered a gasket kit 2 days ago. Back to crassius's question , when I did my leak check I had used carb cleaner and I must admit I didn't try it while the condition was occurring because it would have made it rev even worse. The water I could actually try as it's occurring. Great advice, thank you and I'll be sure to let you know how it turns out.
     
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