New China girl carb problem..help!

Discussion in 'Motorized Bicycle General Discussion' started by nomad69, Feb 18, 2017.

  1. crassius

    crassius Well-Known Member

    Joined:
    Sep 30, 2012
    Messages:
    3,335
    Likes Received:
    33
    excessive smoke often means petcock was left in "on" position while nit running and this will clear up after 20min or so of running
     
  2. nomad69

    nomad69 New Member

    Joined:
    Feb 18, 2017
    Messages:
    27
    Likes Received:
    0
    It ran worse with the lower #jets. I put the 70 back in and lowered the clip to the very bottom. Getting 17-20 mph.

    I've just about had it with kit.!! Been a lemon before I even received it. I don't really care to spend my time tinkering with this pos.

    Should I try a different make carb?

    If so what make/brand and where can I get the carb?

    This will be the last shot, can't afford to waste my life, got better things to do.
     
  3. Potato_In_Exhaust

    Joined:
    Feb 2, 2017
    Messages:
    159
    Likes Received:
    1
    Just get another cheap carb for $5 and see if that will fix it........ don't give up, SON!

    My China beast is running like a top and I LOVE IT, soo much fun. I've lost a few chains but that's due to me not aligning the chain and tightening it properly, other than that the motor is still going strong..... and I've ridden it for hours on stints with hardly any rest for my motor, when I do it's only for a cigarette break and then back on the BEAST, one pedal two pedal dump the clutch and off we go! :)
     
    #43 Potato_In_Exhaust, Mar 7, 2017
    Last edited: Mar 7, 2017
  4. crassius

    crassius Well-Known Member

    Joined:
    Sep 30, 2012
    Messages:
    3,335
    Likes Received:
    33
    it is possible that you have a bad motor, but you should really try to find someone near your location that knows these things.
     
  5. Chaz

    Chaz Active Member

    Joined:
    Jun 3, 2012
    Messages:
    894
    Likes Received:
    34
    If you are using the stock acorn head nuts then maybe you have a leak at the gasket. You can get replacement nuts or just cut the domes off of the stock ones. Then re-torque the nuts.

    The reason the acorn nuts are a problem is that they can bind up at the dome and prevent the nut from going down as it needs to. The cylinder studs are not installed with precision and often are not set to the same depth.

    Also, it is possible that the head itself is not entirely flat. You can cure this by milling/sanding down the contact surface. The method can be found in many threads here in the forum.

    Easiest to start with the head nuts first to see if that fixes your issue. Remember to put the carb settings back to close to stock as you may have "tuned" the carb to run with a leaky head.

    It does sound like you have a leak there.
     
    #45 Chaz, Mar 8, 2017
    Last edited: Mar 8, 2017
  6. Agreen

    Agreen New Member

    Joined:
    Feb 10, 2013
    Messages:
    784
    Likes Received:
    1
    Riddle me this: what do you think the needle's purpose is? (Seriously, I'm not being facetious, I just want to know)

    Also, why did you go to a larger jet? Going down in number size is going up in size.
     
    #46 Agreen, Mar 8, 2017
    Last edited: Mar 8, 2017
  7. Potato_In_Exhaust

    Joined:
    Feb 2, 2017
    Messages:
    159
    Likes Received:
    1
    Yeah, I think he made that mistake. When going down in numbers with jets, it means increasing fuel, meaning a richer fuel mixture..... though I'm not sure if the rule is universal or from carb to carb?

    So to the thread starter, what you want to do is go up on your jet number, to lessen fuel.
     
    #47 Potato_In_Exhaust, Mar 10, 2017
    Last edited: Mar 10, 2017
  8. Agreen

    Agreen New Member

    Joined:
    Feb 10, 2013
    Messages:
    784
    Likes Received:
    1
    Yeah, I really have no clue what the issue is; it's not really clear.

    Keep in mind that the jet affects WIDE OPEN THROTTLE. The needle "modifies" the jet's opening at partial throttle. So if its performance sucks at wide open, change the jet. If it sucks at partial throttle, adjust the needle position. Moving the clip up makes the needle go down in relative position to the slide, making partial throttle more lean. Moving the clip down moves the needle up in relative position to the slide, making partial throttle more rich. Changing the jet size will cause you to change the clip setting. Imagine using your thumb to vary the flow of a garden hose. Then, the fire department shows up and hands you a 3" fire hose and you put your thumb in the same spot to vary the flow. OK, maybe that's a little dramatic, but you get the idea. If you needed to go up in jet size, you may need to change the needle position to a little more lean so you don't flood it out at partial throttle. The inverse is true for going down in jet size.

    If you still don't know if it's lean or rich, try this: While riding, slowly flip the choke on. Does it get better? If so, you need a bigger jet! If it gets worse, it's too rich already and you need a smaller jet.
     
  9. crassius

    crassius Well-Known Member

    Joined:
    Sep 30, 2012
    Messages:
    3,335
    Likes Received:
    33
    NT jets are in mm - a 70 flows more fuel than a 68
     
  10. Agreen

    Agreen New Member

    Joined:
    Feb 10, 2013
    Messages:
    784
    Likes Received:
    1
    mm!? 70mm is almost 3 inches!
     
  11. MotorBicycleRacing

    MotorBicycleRacing Active Member

    Joined:
    Jul 28, 2010
    Messages:
    5,638
    Likes Received:
    19
    #70 drill bit = jet = 0.028" = 0.7112mm Jet size!!!! :D

    #BitSize Inches Millimeters Jet Size

    #80 0.0135 0.3429 34.29
    #79 0.0145 0.3683 36.83
    1/64" 0.0156 0.3969 39.69

    #78 0.016 0.4064 40.64
    #77 0.018 0.4572 45.72
    0.5mm 0.0197 0.5 50

    #76 0.02 0.508 50.8
    #75 0.021 0.5334 53.34
    #74 0.022 0.5715 57.15

    #73 0.024 0.6096 60.96
    #72 0.025 0.635 63.5
    #71 0.026 0.6604 66.04

    #70 0.028 0.7112 71.12
    #69 0.0292 0.74168 74.168
    0.75mm 0.0295 0.75 75

    #68 0.031 0.7874 78.74
    1/32" 0.031 0.7938 79.38
    #67 0.032 0.8128 81.28

    #66 0.033 0.8382 83.82
    0.85mm 0.0335 0.85 85
    #65 0.035 0.889 88.9

    #64 0.036 0.9144 91.44
    #63 0.037 0.9398 93.98
    0.95mm 0.0374 0.95 95

    #62 0.038 0.9652 96.52
    #61 0.039 0.9906 99.06
    1mm 0.0394 1.0 100
    #60 0.04 1.016 101.6
     
  12. MotorBicycleRacing

    MotorBicycleRacing Active Member

    Joined:
    Jul 28, 2010
    Messages:
    5,638
    Likes Received:
    19
    Correct.
    A #70 jet is 0.7mm
     
    #52 MotorBicycleRacing, Mar 10, 2017
    Last edited: Mar 10, 2017
  13. crassius

    crassius Well-Known Member

    Joined:
    Sep 30, 2012
    Messages:
    3,335
    Likes Received:
    33
    jets are in mm at .70mm
     
  14. Agreen

    Agreen New Member

    Joined:
    Feb 10, 2013
    Messages:
    784
    Likes Received:
    1
    :ride:

    (Sorry, arguing semantics is my form of entertainment)

    Anyway, the point is that there are different ways that jets are labeled, so be careful!

    A #70 is close in size to a .70mm jet, but that's the only one! A #68 jet goes up in size, but going to a .68mm jet is going down.
     
  15. MotorBicycleRacing

    MotorBicycleRacing Active Member

    Joined:
    Jul 28, 2010
    Messages:
    5,638
    Likes Received:
    19
    Not semantics, you are just wrong. :)
    Jet are labeled by size in mm and not by the drill bit that makes them.

    100 jet is 1.0 mm
    70 jet is 0.7 mm
    68 jet is 0.68 mm
    34 jet is 0.34 mm

    The jet sizes are the far right column.

    The first column of numbers is DRILL BIT # or size.
    You can't drill all jet sizes with what is commonly available.
    You can drill a 66 jet then jumps to a 71 jet jumps to a 74.

    #70 drill bit = 0.028" = 0.7112mm = Jet size!!!!

    #BitSize Inches Millimeters Jet Size

    #80 0.0135 0.3429 34.29
    #79 0.0145 0.3683 36.83
    1/64" 0.0156 0.3969 39.69

    #78 0.016 0.4064 40.64
    #77 0.018 0.4572 45.72
    0.5mm 0.0197 0.5 50

    #76 0.02 0.508 50.8
    #75 0.021 0.5334 53.34
    #74 0.022 0.5715 57.15

    #73 0.024 0.6096 60.96
    #72 0.025 0.635 63.5
    #71 0.026 0.6604 66.04

    #70 0.028 0.7112 71.12
    #69 0.0292 0.74168 74.168
    0.75mm 0.0295 0.75 75

    #68 0.031 0.7874 78.74
    1/32" 0.031 0.7938 79.38
    #67 0.032 0.8128 81.28

    #66 0.033 0.8382 83.82
    0.85mm 0.0335 0.85 85
    #65 0.035 0.889 88.9

    #64 0.036 0.9144 91.44
    #63 0.037 0.9398 93.98
    0.95mm 0.0374 0.95 95

    #62 0.038 0.9652 96.52
    #61 0.039 0.9906 99.06
    1mm 0.0394 1.0 100
    #60 0.04 1.016 101.6

    Jets for NT carbs are available here.
    http://sickbikeparts.com/carb-jets-nt-dellorto-5mm-main-jet/
     
    #55 MotorBicycleRacing, Mar 10, 2017
    Last edited: Mar 10, 2017
  16. Agreen

    Agreen New Member

    Joined:
    Feb 10, 2013
    Messages:
    784
    Likes Received:
    1
    Well I'll just go ahead and... pull this foot out of my mouth here...

    Ahh, that's better.

    I guess I never made that connection somehow. Maybe because I drill all my own jets and don't fool with buying them. I don't like to wait for shipping :D
     
  17. nomad69

    nomad69 New Member

    Joined:
    Feb 18, 2017
    Messages:
    27
    Likes Received:
    0
    The higher the # the leaner? 70+ or visa/versa?
     
  18. MotorBicycleRacing

    MotorBicycleRacing Active Member

    Joined:
    Jul 28, 2010
    Messages:
    5,638
    Likes Received:
    19
    100 jet is 1.0 mm
    70 jet is 0.7 mm
    68 jet is 0.68 mm
    34 jet is 0.34 mm

    A 34 jet is leaner than a 68 jet because it's a smaller hole.

    The jet that comes with most of the stock carbs is a 70
    Going down to a leaner ~66 jet will make it leaner.

    Also the needle tapers so as you drop it lower by putting
    the clip on a higher notch the opening of the tube is reduced
    making it smaller and leaner.
     
  19. Potato_In_Exhaust

    Joined:
    Feb 2, 2017
    Messages:
    159
    Likes Received:
    1
    For the love of gawd, someone go to the poor sap's house and help him out with his bike! I feel like the guy is on the verge of a mental break down!
     
  20. nomad69

    nomad69 New Member

    Joined:
    Feb 18, 2017
    Messages:
    27
    Likes Received:
    0
    Ahhhhh... I'm not about to break down, 20mph on 2nd tank full... I'm 245 with 50 cc bike, i'll tune it right, it ain't my first china bomb.

    I'm looking for a muffler clamp that fits a 3 inch mountain bike frame?
     

Share This Page