engine sputters, hard to turn over

Discussion in 'Motorized Bicycle Trouble Shooting' started by domster66, Jun 20, 2012.

  1. domster66

    domster66 New Member

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    Hi I already posted about my idling problem, but I'm also wondering what could be wrong with this new problem...... So I will ride downhill and the engine will sputter and sputter until finally it starts up, I run out of road, engine shuts off, then it takes SO MUCH leg power to get it turned over and running... I really need to know why this won't turn over easy. I seriously need like full energy and a quarter mile... Please answer and give me tips, I know other people have already asked this on other threads but those aren't really working for me, I need something specifically to my bike. I have taken the carb apart and made sure it was squeaky clean! I also have some pics of the bike... It's an 80cc china engine(great...) and I just don't know what to do to make it turn over easy. I am very tired and out of breath. Thanks!
     
  2. GearNut

    GearNut Active Member

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    Severe air leak is my first suspicion.
     
  3. domster66

    domster66 New Member

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    what do you think the best way to check for air leakage... Like should i get it started, hold the clutch in while giving it gas( because it doesnt idle) and then spray carb cleaner? or what...
    Thanks for responding!
     
  4. GearNut

    GearNut Active Member

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    That is a good way to check for air leaks.
    You can use tape, mechanic's wire or a bungee cord wrapped around the clutch lever and hand grip to hold the clutch lever in for you. That makes things easier.
    Hold the throttle so the engine is running at the slowest speed you can get it to run at.
    Spray where the carburetor attaches to the manifold and also where the manifold attaches to the cylinder. If the engine speed suddenly slows down or increases you found the leak. Don't over do it with the spraying though. If any gets sucked into the air cleaner it will give you a false reading.

    Looking at your pics of your bike I see that you have an "NT" carburetor.
    Here is a good thread concerning a common air leak with that particular carburetor.
    Thought and Observations- Air leaks
    I only add that Seal All is quite possibly the easiest and most durable sealant to use.
    Click here for seal all description
    Good luck, and let us know the outcome.
     
  5. domster66

    domster66 New Member

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    Thanks, I took a good look at where the carb air intake gasket is, and it is just totally beat up, so I think maybe it could be leaking there,so i ordered a new gasket, also, I ordered a SkyHawk CNS High Performance Carburetor from King's motor bikes, so hopefully that helps. I will also try the carb cleaner spray test when I get the chance. Thank you for responding, I will get back to see if it solves these problems. Oh and I ordered a new spark plug too.
     
  6. GearNut

    GearNut Active Member

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  7. domster66

    domster66 New Member

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    yeah i have been reading a lot about them on the forums and quite frankly, I'm a bit nervous! A lot of people are having lots of problems with them.. but this isn't the first time we've had to handle things that are crap out of the box, but i'm just gonna have to find out when I get it tomorrow. But i'm just hoping it will be an improvement because I really think the NT carb I have now is just really screwin' this bike... Can't get it started without going down a mountain, doesn't run right, sputters, won't idle... so i'll keep you posted.
     
  8. domster66

    domster66 New Member

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    OK so I got the new carb and other stuff... I installed it and tried getting it going and it will not even try starting at all.... not one bit. I will go downhill at least 20mph, giving it gas and everything, And it will just not budge. Then I took a look at the float and everything, and now its dripping like crazy.... Sigh... Any help, besides throwing it out? I heard maybe my float is upside down... But what do I do after that's fixed?? Why wont it do anything?????
     
  9. GearNut

    GearNut Active Member

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    You need to start with the basics for a no start engine with known good compression.

    1. Use fresh gasoline, not gas that has been stored for a month.
    Modern gas is not really gas anymore, it just has the same name (marketing scheme).
    It has alcohol in it which readily absorbs water from the atmosphere. It also has different additives in it which break down faster than gasoline and cause the gasoline to go stale faster. All this is a double negative whammy for storing it, even inside a sealed container.

    2. *No air leaks allowed!*
    Check all manifold connections for air leaks. Also double check that all vent/ vacuum hoses are connected/ routed correctly.

    3. Insure that the fuel control is working perfectly: Fuel valve flows sufficiently. Carburetor float setting is at the correct height and shuts off the flow completely when the correct fuel height is achieved. (If the carburetor flows fuel out of anywhere while just sitting there with the fuel valve in the on position it is flooding the engine with gasoline.) It also needs to allow sufficient flow into the float bowl to replenish the fuel as needed.

    4. When trying to diagnose initial jetting, the spark plug can tell a good tale.
    If it is wet there is too much fuel being added to the air or...
    This also could be a sign of no spark, so check that too and rule out the possibility of a no spark condition before tearing into the carburetor.
    Also replace the spark plug with a new one or a known good working one.
    A spark plug can spark plenty good just resting on the outside of the engine, but the conditions inside a combustion chamber under compression pressures are totally different and a spark plug can fail when put under these demands.
    Assuming that the spark is dependable;
    Wrong, (too large) jetting, an enrichener (that is what the CNS has instead of a choke) that does not seal when turned off or too high of a float setting can cause the carburetor to mix too much fuel to the air.

    4. If the spark plug is dry then there is not enough fuel being added to the air.
    This could be related to #2 or #3 above, which is why you check those first.
    It also could be a sign of a clogged fuel jet or passage inside the carburetor.
    This being a brand new carburetor, don't overlook it and think that all is well!
    Sometimes manufacturing debris can get left inside where it does not belong.

    If all the above checks out good then it is time to try a different carburetor.
     
    #9 GearNut, Jun 26, 2012
    Last edited: Jun 26, 2012
    D.Knight likes this.
  10. domster66

    domster66 New Member

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    Thanks, tomorrow it looks like I'm gonna be on another quest of testing all these problems until I fix it and come across another problem... I think I will start by adjusting the float and pin thing( the part that looks like a pin connected to the metal ring in the bowl) by maybe barely bending some metal to that it won't let as much fuel in.
     
  11. domster66

    domster66 New Member

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    Also I see you live in SD like meh. Do you know the M bike laws around here? Do I need a license or can I just ride on the bike lane or what...? It doesn't seem like people really know what the answer is...
     
  12. bigbutterbean

    bigbutterbean New Member

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    I have never used a cns carb (and never will after all I have read about it), but a lot of members here say it is a tuning nightmare. Only a few members here have ever said they have gotten the cns carb running good without spending a whole lot of time trying to tune it. I run the nt carb myself, and it really isnt that much trouble to tune. The only problem I ever had with my carb was that the spring behind the idle screw would always eventually wear out. I finally solved the problem with a small piece of rubber fuel line and a zip tie. I cut the fuel line lengthwise, fit it over the idle screw and zip tied it on. it keeps the idle screw in place, but is loose enough to allow easy adjustment. If I ever do upgrade my carb, and I might, it will be an r/t carb from thatsdax (www.thatsdax.com). Honestly, the money you spend on the rt carb will be worth saving the hassle of trying to tune the cns carb, at least imho.
     
  13. Toadmund

    Toadmund New Member

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    Hi, broken record here!

    Because it's so hard to turn over and hard to start, make sure your clutch plate is not slipping, check for adjustment.

    The stalling could be a separate problem.
     
  14. domster66

    domster66 New Member

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    Sweet! I finally got it up and running great!!! But there is a new problem...So I guess it's not all great. But first, what I did was flip the float since it was upside down and got the gas working properly... But still, no success... Until I checked my spark plug, and realized it was wet, So that had to be it! So, I put on my new spark plug, pedaled about 10feet and BAM! Off and running like a champ! But here is the new problem... I have no control over the throttle!!! It will start(without a sweat might I add :) ) But will just go and I cannot do anything but just break. Also, My killswitch is disconnected, because I don't know how it connects... There are two wires running from the killswitch- One red and one black. Before on my other killswitch, it had one cord leading down that was black, that connected to a white cord. Anyone know this connects? And why I have no control over the throttle? Should I post this in a new thread?
    Thanks!
     
    #14 domster66, Jun 26, 2012
    Last edited: Jun 27, 2012
  15. GearNut

    GearNut Active Member

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    Throttle control problems... sounds like the tuning process needs to begin now that the engine actually runs.
    Will it at least rev up or is it a rev to the moon problem?
    ____________________________

    Wiring is easy the colors do not matter which color goes to which wire. Just wire one kill switch wire to the blue magneto wire and the other kill switch wire to the black magneto wire. Use quality connectors, not the cheap krap connectors that came with the engine, and seal them with electrical tape or solder the wires with no connectors needed and seal them with heat shrink tubing.
    ____________________________

    California law, read this thread: The Real Deal on California Law.
    bairdco covers everything on the very first post. The rest of the thread is just to read if you wish to. Warning: If you read the rest of the thread, some confusion is in there too.
    If you want to know the law as California says it, do a google search for "CVC 406a"
    Also you can read this thread for reference purposes: California Motorized Bicycle Requirements
    ____________________________

    Should you post a new thread for the new throttle problem?
    I vote for no.
    Lets keep it all in one thread as it still relates to the carburetor and the whole thing is easier to follow along with if kept in one continuous thread.
     
    #15 GearNut, Jun 26, 2012
    Last edited: Jun 26, 2012
  16. wan37

    wan37 Member

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    Okay here you go the kill switch first connect one wire to black and the other to blue It does not matter which one's just do not use white wire from motor.I would say on the running part is that you got a big air leak or throttle is not right in the carb...the slide barrel is in backwards.
     
  17. domster66

    domster66 New Member

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    Wow GearNut! Thanks for the very detailed reply on all those questions I asked! I see you read completely through my posts :) . So on with it now... Well, I have something very strange, unless you have seen it before, IDK.... But I have found out that for some reason the thing that I supposedly thought as a choke that mounts on the right side of the handlebar next to the throttle is actually the throttle itself! And what is supposed to be the throttle is actually the choke(maybe they messed it up? Idk didn't come with instructions).Now isn't that something... So now it looks as if I have to adjust the new 'throttle', adjust the idle, and hook up the kill switch so I can kill it (So far I can just kill it by holding on the bike letting the clutch out slowly and it will die in a few secs, since I haven't set up the idle). If I run it and try using the throttle, it won't really do much besides lose some power. If I use the 'new throttle', it acts a lot like how the throttle should. Adjusting it may take a bit of time, I can't say for sure but will check tomorrow. Maybe I'm wrong but here is a pic of the "new throttle"(thing next to the throttle), and the actual throttle. If you have the real name of what it is actually called that would be very much appreciated. So what do you think? zpt
     

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  18. domster66

    domster66 New Member

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    Well, it doesn't matter now. I just put on the old carb and it is working fine. The CNS carb was just too much and was too complicated. But hey, it could always be used as a spare!

    So, it turned out just to be an air leak, and a bad spark plug. So, thanks again for all the help guys. My advice and everyone else's is just go with the NT carb. Also, if you ever buy a pre-made motorized bike off Craigslist make sure it completely works first before buying it!!! LOL! But, I'm riding happy now, it won't quite idle, but I can just hold in the clutch and let it go and it will go when I need it to. Also now it starts up tons easier too so everything is good. See ya'll later!dance1
     
  19. GearNut

    GearNut Active Member

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    I am glad to hear that you at least got the engine to run satisfactorily, no matter which carb did the trick. Enjoy the ride and be careful! Cars may see you and maby even acknowledge that you are riding a bicycle. They often will plan their turns and stops in front of you expecting a bicycle to be traveling at 10 to 15 MPH, not 25 to 30 MPH. Plan for defensive riding tactics!
     
  20. robdawgg

    robdawgg New Member

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    Hey everyone im having sort of the same problem. My engine turns over with a little difficulty but when I twist the throttle, it doesnt accelerate at all. I have the same engine. 80cc china motor
     

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