running rich or lean??

Discussion in 'Motorized Bicycle Trouble Shooting' started by WaterDog, Oct 11, 2010.

  1. WaterDog

    WaterDog New Member

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    Ok, my bike runs fine, well I assume so because I've only rode my own. Low and mid range acceleration is great, but it seems to hit a wall near the top end. It almost feels like a limiter is installed or maybe the engine chokes a little. I ran out of gas today and had incredible power and speed between the sputtering. So I assume I had a temerary lean condition (lean means more air correct?). So I was wondering how I can adjust my lean/rich mixture to find the ideal ratio. Is there a screw or something similar to the idea speed screew? I do have the high flow K&N style air filter and regular muffler.
     
  2. Bikeguy Joe

    Bikeguy Joe Godfather of Motorized Bicycles

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    Sounds like you are rich on the top end. If it four strokes when wide open near top rpm, and runs way better when you run out of gas, it is generally too rich. Only a "plug chop" will tell fo'sho'. Clean the plug thoroughly, then put it in, and after warm up run it wide open for a minute or so if you can stand the vibes, then pull the clutch and cut the engine off.

    If the plug is black/wet/oily, you are too rich.
     
  3. WaterDog

    WaterDog New Member

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    thx...ok, so once I determine rich or lean, how do I correct it? The engine is relatively new so I am running 25:1 synethic right now. Is there an adjustment screw or how exactly would I adjust the rich/lean?
     
  4. Nougat

    Nougat New Member

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    Unscrew the carb top and remove the throttle cable from the slide. There's a long pin - the needle - with a little e-clip on it. Stock, that clip is in the middle of five notches. Move it to the second notch from the top. This lets the needle sit lower in the emulsion tube, which has the carb run leaner between about 20 and 80 percent throttle.

    The only way to make it leaner at full throttle is to replace the jet with a smaller one.

    If you're still breaking in, I wouldn't worry about it too much. Wait till you've got a couple hundred miles on.
     
  5. WaterDog

    WaterDog New Member

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    Perfect, ill try adjusting the e-clip. But considering it runs pretty good in the 20-80% of throttle, maybe the jet could stand some adjusting. Wouldn't it just be better (and easier for a newbe) to buy the racing carb? They're not that pricey and I assume these mods have already been done.
     
  6. Dave31

    Dave31 Moderator
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    You will still need to tune it for your engine, some get lucky just bolting them on but chances are you will still have to do the same thing.

    I tune my carb using the needle and jet. I also tune for 1/4, 1/2, 3/4 and full throttle to get the best performance.
     
  7. isthisreal1991

    isthisreal1991 New Member

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    :-|| I know I'm a little late but I have questions... I just signed up for this thread and I'm having the EXACT same problems but IM a noobie so I need more help and I can't figure out how to post a thread on this site for this please help me mainly on how to make a new tread I can't figure it out.
     
  8. decoherence

    decoherence New Member

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    you know where you clicked "new post"?
    one page back in the same spot is "new thread".

    if you have the same problem, the answer given above is pretty much simplified instructions.
    no need to start a new thread.
    what part do you not understand?
    that part can be explained further.
    if you want to know something like the "plug chop" mentioned, you can use the custom search @ the top.
    just enter plug chop.
    it will pull up relevant posts.
    most questions have been covered many times & can be quite helpful.
     
  9. Maxvision

    Maxvision New Member

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    One way to tell if you're running rich or lean is to run you bike full throttle for a while then shut the motor off and look at the spark plug. Black plug = rich, light tan = lean, light brown = just right.

    I run my bikes lean causer I love to hear them scream. But I go through lots of head gaskets and cylinders.
     
  10. isthisreal1991

    isthisreal1991 New Member

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    haha i still cant find out how to post... but um yea so my plug is always covered in oil i dont know if im confident enough to take a part the carb to mess with the needle and also i have the upgraded carb for the 66/80 cc with no primer just one screw on one side which i belive is idle and 2 really small scres on the other side and i dont know how to tinker with them ... after 4 min of running if i WOT it boggs i can do about 60% throttle on flat ground
     
  11. Maxvision

    Maxvision New Member

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    When I was 6 years old my daddy told me "if you can take it apart, you'll remember how it goes back together". I've been taking things apart and putting them back together ever since.

    You don't have to take the whole carb apart to adjust the needle, Just unscrew the top where your cable goes in and pull the throttle slide out. You'll see the needle hanging out the bottom of the throttle slide. Just pull up the spring and the needle will come right out along with a little slotted disk that goes on top of the needle to hold it down in the slide. Pull the clip off the needle with a pair of pliers and move to the top most notch closest to the dull end of the needle. Put it all back together and try that.
     
  12. CTripps

    CTripps Active Member

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    Digital cameras and/or camera phones are great when it comes to working in 'new territory'. Take a pic, take something apart, and repeat until you get to what you're after. Reassemble by following the pics in reverse. Just have a clean, clear area you can lay the parts out on as you go.

    For this though, go with Maxvision's advise, it's really not that tricky. Just don't drop the e-clip, they love playing hide-and-seek if they get a chance.
     
  13. isthisreal1991

    isthisreal1991 New Member

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    You guys are awesome thank you very much I am getting more aquinted with this forum now and managed a post haha
     
  14. maniac57

    maniac57 Old, Fat, and still faster than you

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    E-clips also known as "Jesus clips" to us old timers...as in "JESUS!, where did that clip fly off to?"
     
  15. Maxvision

    Maxvision New Member

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    JEZUS, good thing I can get another clip at Home Depot instead of having to have one sent all the way from China.

    Small pair of vice grips will help prevent that. If you only have a cheap one you can sharpen the grip end so it will get a good bite on the clip.

    JEZUS, be careful not to bend the brass needle while taking the clip off or putting it back on.
     
  16. nightcruiser

    nightcruiser New Member

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    For the original poster, as someone has already noted, at WOT (Wide Open Throttle) the man jet is responsible for the mix, the needle controls the mix in the mid throttle region. If you are looking to effect the way your bike runs at WOT you would need to either adjust the main jet size, or adjust the air flow by tuning the muffler and/or air filter.
    One thing I haven't seen mentioned here, if your carb is not mounted level you might benefit from doing a little float adjustment. Sometimes when a carb leans in toward the motor it can make it run rich, adjusting the float to maintain a LOWER fuel level in the bowl may help lean out your mix a bit and give you a bit more power at WOT.
    For the newbie that is reluctant to take apart his carb and tune it... You're gonna have to take it apart sooner than later just to clean it, so might as well bite the bullet and dig in! There aren't many parts inside and it's not that complicated (to assemble at least, understanding how it actually works is another thing). Just make sure you work on a clean workspace and keep track of the few small parts from inside. Taking pictures with a digital camera as you rip things apart is also a good suggestion also....
    This is a hands on hobby, these Chinese motors are not particularly reliable, if you don't know how to work on them you probably wont be riding long... When I first started out I read someone here say you should have desire to dig in and work on your bike, if you don't have that desire then you should probably just buy a scooter. I didn't understand at the time, but now I do. If you don't enjoy wrenching on your bike this is gonna be a miserable experience for you, if you just want cheap fuel efficient transportation then a scooter is more appropriate....
    I'm not trying to say anyone here should go the scooter route, just trying to say that wrenching is REQUIRED on a home made MB, but not on a scooter. If you ride a MB get used to wrenching, embrace it! LOL

    PS I don't recall seeing noted what kind of carb you guys are running, that makes a big diffrence as the NT or Speed carb only has one jet while the CNS carb has three....
     
  17. motorized kodiak

    motorized kodiak New Member

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    i think i am running my bike to rich, it doesnt start up, what should i do?
     
  18. crassius

    crassius Active Member

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    too rich shouldn't keep it from starting unless you mean too much oil in the fuel
     
  19. nightcruiser

    nightcruiser New Member

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    Pull your spark plug, turn over the motor a few times with the plug out (make sure you do not have flame or spark near the plug hole to ignite any gas that may come out). Dry out/clean your spark plug or preferably install a new plug. Hopefully your motor will start, if it does then make sure you turn off the fuel valve when the motor is not running.

    If it is actually running too rich then my first stop would be to make a float adjustment. Bend the tab on the float so the needle valve closes with the float LOWER in the bowl (so the carb will hold LESS fuel in the bowl). This tends to lean out the mix. If still too rich you would have to either adjust the air flow (air filter and/or muffler) to allow air to flow easier, or change your jet to a smaller size....
     
  20. isthisreal1991

    isthisreal1991 New Member

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    Thanks guys I figured it out =p
     

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