Bike wont start after fixing air leak

Discussion in '2 Stroke Bicycle Engines & Kits' started by ninjaplatypus42, Apr 25, 2017.

  1. ninjaplatypus42

    ninjaplatypus42 New Member

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    I've been having trouble getting the carb to fit on this bike so I've gone through a few different extensions and bent intakes to get it to fit. I finally found one that works after some persuasion with a propane torch and a pipe wrench. Anyways there was a small leak where the exhaust clamps to the carb and i had to wait a couple weeks to get an o-ring to stop it. In that time it ran well and would start on the second or third pedal (I have a shift kit). I put the o-ring in and now it won't start. I've got it on the leanest c-clip setting right now and have tried all the others. I can sometimes get it to start for 30 seconds or so with a high idle and as son as i try to adjust the idle lower it dies. I'm completely stuck at this point.
     
  2. TheNecromancer13

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    What carb are you using?
     
  3. ninjaplatypus42

    ninjaplatypus42 New Member

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    Stock NT carb.
     
  4. crassius

    crassius Well-Known Member

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    nt doesn't take an o-ring - seen them get sucked into motor when tried
     
  5. ninjaplatypus42

    ninjaplatypus42 New Member

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    I know it doesn't take one stock but without it it leaks. I've talked to people that insist on running them with a o-ring for a better seal. I don't see how it could get sucked into the engine its pretty much clamped in place by the intake.
     
  6. ninjaplatypus42

    ninjaplatypus42 New Member

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    So far I've tried starting it with no, half, and full choke and also no throttle some throttle and all throttle for each c-clip position. I've checked the float and it's fine, the jet is screwed in properly, the float tangs aren't bent, there is no air leak anywhere else on the engine i checked with carb cleaner. I'm really stumped.
     
  7. Tyler6357

    Tyler6357 Member

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    It sounds like it might be an air leak. Just because it's not leaking fuel doesn't mean it doesn't have an air leak. Check the intake/carb connection as well as the intake/intake manifold connection and gasket. Also, check around the head at the head gasket. Make sure the head bolts are torqued down to 14 foot pounds. If you can get it started you can usually feel air shooting out from around the head if the leak is small enough to get it to start. Air leaks cause power loss and idling problems and real bad ones cause no a start condition.
     
  8. ninjaplatypus42

    ninjaplatypus42 New Member

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    As i said i checked thoroughly for air leaks in the rest of the engine everything is sealed up tight. I wasn't referring to fuel at all just air leaks.
     
  9. crassius

    crassius Well-Known Member

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    the carbs that need an o-ring have a plastic insert in them that captures the o-ring - without it, the o-ring can soften and drop into the intake

    as far as the main problem goes, I'd first put all back to when you had the air leak and see if it still starts like that - if not, something else has changed since then

    do not forget that the base gasket can cause an air leak also, and this can often be fixed by lifting the barrel slightly and soaking gasket in 2-stroke oil before retightening
     
  10. Kioshk

    Kioshk Active Member

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  11. ninjaplatypus42

    ninjaplatypus42 New Member

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    Base gasket is the one between the cylinder and the bottom end?
     
  12. crassius

    crassius Well-Known Member

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    yes - a leak there can be spotted by misting water in the area - when I check for air leaks, I usually hold a piece of cardboard over other places to isolate the spot that makes the difference
     
  13. ninjaplatypus42

    ninjaplatypus42 New Member

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    The problem is i can't get it started to test for leaks. I tested it for leaks before it stopped starting and it was only at the carb. Is there any way to test for leaks without it running?
     
  14. ninjaplatypus42

    ninjaplatypus42 New Member

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    It's not starting without the o-ring either now so there's that. I've got strong spark, compression, even fires a couple times on its own every now and then when i try to start it.
     
  15. crassius

    crassius Well-Known Member

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    I'd guess you're not getting fuel, but check by putting some through spark hole.
     
  16. Tyler6357

    Tyler6357 Member

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    People have been using O ring gaskets for years on stock NT carbs, they work, I don't think it's that. If it's leaking gas without the O ring, you should use the O ring.

    Did you check the crank seals? Open the magneto cover, do you see oil in there? How about the clutch side? Sometimes the rubber seals can come loose or get damaged and leak. They have been known to shake off and often times just adjusting how they fit can seal them back up but if they are chewed up they are a cheap replacement part ($6). Sometimes they get shifted and get chewed up however if they are chewed up because the crank is bent than new seals will get chewed up too. If the magneto wobbles when you crank the engine it could indicate a bent crank.

    If the crank seals look ok, the next thing I would check is the carb. Is gas flowing good though it? Is the spark plug wet after you try to start it? You could take the carb off and clean it, maybe something is stuck in the jet or something. The higher the needle clip is the leaner it should be, I'm sure you have messed around with that, I guess you could try a bigger or smaller jet. When it did start, was it smoking or anything? Also, have you checked the exhaust pipe? Is it clogged with oil? A change in back pressure will have an effect.

    If that all seems good, next I would check all the electric parts with a meter (coil, wires, cdi, magneto, etc..) Disconnect the kill switch and see if it will start.
     
    #16 Tyler6357, Apr 26, 2017
    Last edited: Apr 27, 2017
  17. ninjaplatypus42

    ninjaplatypus42 New Member

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    crassius, ill check fuel flow tomorrow that was the next thing on my list. Tyler again, its not leaking oil. Its leaking air lol i will check all the seals any ways though.
     
  18. crassius

    crassius Well-Known Member

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    I'm just a repair shop, so don't see the ones that work - see a crapload that don't work tho : )

    in real machinery, one never sees an o-ring that isn't captured in some type of channel - with these motors, I've seen a lot that were captured in the intake port, and chunks captured in the exhaust port, and some captured as black smears on the cylinder walls
     
  19. Tyler6357

    Tyler6357 Member

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    Alright, you should know. I was just reading this sticky thread here that recommended using them. Myself, I prefer Delledo clone (RT) type carbs. They come with a plastic seal.
     
  20. ninjaplatypus42

    ninjaplatypus42 New Member

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    Crassius it is in a channel of sorts, im not sure it's what you mean by channel though. The one i use is the same size as the OD of the intake pipe. And there's that lip in the carb that the intake would normally sit against and the oring just gets sandwiched in between the intake pipe and that lip. I'd imagine if someone used an oring not designed for gas it would deteriorate and fall to pieces, maybe that's whats happening with the ones you're seeing.
     

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