4 stroking at 0 throttle-1/4 throttle

Discussion in 'Motorized Bicycle General Discussion' started by fischer550, Jun 1, 2014.

  1. fischer550

    fischer550 Member

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    Engine: dax bottom end with fred stage 2 top end kit.
    Plug:B8HS-10
    Exhaust: Torquer 2 from arrow
    Jet size:66 from SPB
    Carb: NT
    C-Clip position: top notch (leanest)
    Mix ratio: about 26:1

    Brand new engine, I am trying to take it easy so I am riding at very low rpm's and it 4 strokes really bad but once I open the throttle a bit she soars. Any suggestions?
     
  2. fischer550

    fischer550 Member

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    Also important, I am at elevation 5,000 ft.
     
  3. crassius

    crassius Well-Known Member

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    give it time for the rings to seat - you're probably blowing half your fuel back into cases for next load
     
  4. fischer550

    fischer550 Member

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    What does that mean? haha
     
  5. xseler

    xseler Well-Known Member

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    The piston rings haven't worn enough to completely seal against the cylinder wall.

    Until you've run at least 2 to 3 tanks of fuel through this engine, it'll continue to do weird/random stuff. Now's not the time to try to get everything perfect to your satisfaction. Just ride it like you normally would with the exception of extended wide open throttle runs.

    Good luck and exercise a bit of patience......I bet that everything will turn out just peachy!
     
  6. rogergendron1

    rogergendron1 New Member

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    Also make shure your running a correct mix of 32:1 to 50:1 oil to gas

    then once you have a good mix of say 32:1 in the tank and running then tune the carb

    first make marks on the twist throttle for
    wot
    half throttle
    1/4
    3/4

    Once you mark those trottle positions make an arrow on the throttle so it points to the positions wile deiving so you can see where your throttle is and how mutch its open wile riding

    if your 4stroking at 0 to 1/4 then its on the idle jet and your air idle screw need to be adjisted , try 2 1/2 turns oit from closed if it stil fourstrokes after more than 2 1/2 turns oit you need a smaller idle jet
    Closed to 1/4 is the iair idle screw
    1/4 to 1/2 throttle is the idle jet
    1/2 to 3-4 is the slide needle and slide cutaway
    3/4 to wot is the main jet

    thats an easy way to see what jet your on wile rideing and how it needs to be tunned
    1
     
  7. GearNut

    GearNut Active Member

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    In another thread you stated that the carburetor is sitting at an extreme angle.
    How extreme is it? The carburetor can tolerate a little angle, but extreme angles upset the level of fuel inside the float bowl and that will cause all sorts of unwanted problems. Can you post a picture of it, camera sitting perfectly level to show clearly the angle of the carburetor?
     
  8. mapbike

    mapbike Active Member

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    Not sure what your problem is but if it wasn't acting up before this problem and you haven't changed anything, then it has nothing to do with fuel mix or carb angle and if it only 4 strokes at low rpm that isn't that uncommon and wont hurt a thing, just put some miles on it keeping an eye on drive train and all mounting hardware.

    I will say that going to 32:1 mix could help the issue some but if you do change mix be sure to check the plug after a few miles just to make sure you dont get to lean, most likely it wont be but never hurts to double check.

    Another thing to remember is it make absolutley no difference what lower you have or what upper you have blah blah blah...... the same tuning techniques apply to any china girl you have....

    One more thing ai will add is that 99% of the time having the c clip on the second from the top notch is whete it needs to be and then correct carb jetting will get the tune where it needs to be, you proba ly need a smaller main jet onceyou get some more time and miles on the engine but for now I'd just run it and let it break in a bit more before making more changes if it will maintain a comfortable cruise speed you can live with until it loosens up and settles in a little better.

    Map
    .wee.
     
    #8 mapbike, Jun 2, 2014
    Last edited: Jun 2, 2014
  9. fischer550

    fischer550 Member

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    heres a picture of the carb angle. I did change the stock jet size to a 66, and I went on a 3mile ride and it went just fine and then out of nowhere the surging began and now it does it all the time.
     

    Attached Files:

  10. crassius

    crassius Well-Known Member

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    frame seems made for the intake that comes with engines - not sure why maker of that manifold wouldn't offer one that sets the carb level, but looks like you have plenty of room to add a bend

    when I don't have any other hose handy, I warm up a piece of garden hose to stretch it wider a bit & paint it black : )
     
  11. fischer550

    fischer550 Member

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    But do you think this is a problem?
     
  12. mapbike

    mapbike Active Member

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    Honestly just not sure what you mean by surging, is it as if you are giving it throttle and then letting off giving again and letting off giving again and letting off......?

    A surge and a 4 steoking engine are two completely different things, sounds like your engine ma be starving for fuel, remove hose from carb and see if gas flows good and quickly for fuel valve when you open it.

    Is your fuel cap vented...?

    Take the bike for a ride, if it starts the "surging" reach down and loosen the fuel cap on tank a little so it can breathe and see if the surging stops, if so you need to vent the cap.

    The carb angle you have is excellent, I have had carbe at wa more of an angle than yours and never had a single issue with fuel, if float isn't set right in carb the carb angle will become an issue but when float level is as high as possible without causing carb to flood, the angle isn't that important in my experience.

    Map
     
  13. rogergendron1

    rogergendron1 New Member

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    if it started surging out of nowhere you have an air leak ... check the intake manifold gasket and make shure the carb is clamped tight to the intake
     
  14. fischer550

    fischer550 Member

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    I have a boost intake its actually not gaskets but ratherusesa sealant, it came with the cyclider already installed
     
  15. fischer550

    fischer550 Member

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    and map even if i am at 5,000 ft would you still recommend the c-clip being not at the top but second?
     
  16. fischer550

    fischer550 Member

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    oh one ore thing, I did unscrew the gas cap when it started to surge and I do believe it started working because of that. I have the sky hawk frame with its gas cap provided.Are stock gas caps vented?
     
  17. rogergendron1

    rogergendron1 New Member

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    The gas caps are not vented , you can drill a 1/6th hole in the center theough the cap to prevent vacume pressure build up
     
  18. mapbike

    mapbike Active Member

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    Well, after reading the last posts you made here it sounds like the gas cap not venting may have been your trouble, so if that solved it and you feel it starts easy enough and is running good at low to mid rpms with clip at top groove then just leave it there, wont hurt a thing and at your elevation that may be where yours works best on your engine set up.

    I've never had a Grube frame but it seems that the gas caps are fairly small when I've seen them in pictures of the frame, if it were me and there is enough room on cap which I think there is.... get myself an 1/8' NPT pipe tap, drill the correct size hole through the cap and thread in a small barbed brass fitting that I could put a small length of tubing on so the cap can vent good.

    Drilling a 1/16" or so size hole through cap may work out just fine also, but the fuel tank has got to vent or you will have fuel supply issues, which can come in the form of surging and seeming as if it is running out of gas.

    Map
     
  19. fischer550

    fischer550 Member

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    Gotcha, except if stock tanks are not vented, why does mine have to be?
     
  20. CTripps

    CTripps Active Member

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    Sometimes they forget and actually use a good O-ring on the neck of the cap. ;)
     

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