New China girl carb problem..help!

[nomad69]

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.

 

[Potato_In_Exhaust]

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!

 

[crassius]

it is possible that you have a bad motor, but you should really try to find someone near your location that knows these things.

 

[Chaz]

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.

 

[Agreen]

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.

 

[Potato_In_Exhaust]

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.

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.

 

[Agreen]

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.

 

[crassius]

NT jets are in mm - a 70 flows more fuel than a 68

 

[Agreen]

mm!? 70mm is almost 3 inches!

 

[MotorBicycleRacing]

mm!? 70mm is almost 3 inches!

#70 drill bit = jet = 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

 

[MotorBicycleRacing]

NT jets are in mm - a 70 flows more fuel than a 68

Correct.
A #70 jet is 0.7mm

 

[crassius]

jets are in mm at .70mm

 

[Agreen]

(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.

 

[MotorBicycleRacing]

(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.

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/

 

[Agreen]

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

 

[nomad69]

The higher the # the leaner? 70+ or visa/versa?

 

[MotorBicycleRacing]

The higher the # the leaner? 70+ or visa/versa?

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.

 

[Potato_In_Exhaust]

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!

 

[nomad69]

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?

 

[Chaz]

You are making progress. You'll have to make your own clamp. Two hose clamps and a length of metal bent in a Z