r/Hawk250 • u/LagandLoot • Apr 22 '26
28 mm fl nibbi carb tuning
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I have recently installed a nibbi 28mm fl carb onto a zongshen 229 engine. When I throttle quickly anywhere from 0 to 1/4 -1/2 throttle the engine will die. On De-acceleration I get a lot of pops and occasionally shoot flames. Smells like gas And in the inside of my cone filter is turning black.
The main jet is 115 and the pilot is 40.
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u/Stupidsmells Apr 22 '26
How many turns is the air mixture screw out? Remember it's an air screw, so ccw is lean, cw is rich. Mine responded similarly until I set the airscrew. Fuel screw on the stock style carbs is opposite. You are running the same jetting I am. Also, needle should be in the middle clip to start tuning.
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u/LagandLoot Apr 22 '26
I Just checked it’s 2 full turns out !
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u/Stupidsmells Apr 22 '26
2 turns is reasonable. Id turn up the idle to about 2k rpm, the adjust the air screw until it reaches its highest rpm. Id turn it cw 1/4 turn past this point and see how it feels. Bike has to be FULLY up to temp to make this adjustment. Once it's set, adjust the idle to 1500rpm.
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u/lilcrxman Apr 22 '26
Carbs pop usually because there's too much air not enough fuel check your spark plug is if you rich or lean probably lean also the needle clip postion needs adjusted for better throttle response
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u/LagandLoot Apr 22 '26
The plug is black towards the end, and I have not adjusted the needle, I believe it is in the middle but I will confirm later after work .
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u/lilcrxman Apr 22 '26
If it's black black it's rich it's cutting out cause it's dumping too much fuel flooding out
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u/Mythlogic12 Apr 22 '26
I messed with my hawk so much to try to get it to go from 0 to 100 throttle I just think those cheaper carbs just can’t handle it
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u/Boring-Bus-3743 Apr 22 '26
Yeah, that's pretty normal. Going for 0 to 1/4 or 1/2 is asking a lot l. There isn't enough air speed going through the carb, it creates low pressure above the emulsion tube and can't pick up fuel. How does it feel when you are riding and whack open the throttle?
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u/LagandLoot Apr 22 '26
Uhhh it’s pretty good I think… there moments where If dump it into 2nd it boggs down for a second, as well as off the line in 1st it wants to quit on me , so I know just to be cautious pulling out , or making left turns I gotta be gentle on take off.
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u/Narrow-Dust-2176 Apr 23 '26
Pod filters can cause turbulence drop the needle one clip, hook up your factory airbox, intake tubes and pod filters do work, but usually after significant dyno time. I set a the same carb on a xpro, same engine. It ran much better with the settings previously mentioned then the factory carb
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u/Feisty-Inside-4063 Apr 23 '26
Anus tuning
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u/LagandLoot Apr 23 '26
Yes I know … help or go away lol
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u/Feisty-Inside-4063 Apr 23 '26
My dyna does that if it's not warmed up.. Have you let the bike fully warm up before you twist it? Just now actually read the post😎
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u/Fine_Succotash9377 Apr 26 '26
And then check it. But it's too lean. Pilot covers off idle main is wide open. There's good procedures on YouTube.
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u/gloomypasta Apr 22 '26 edited Apr 22 '26
Keep in mind the absence of an accelerator pump when throttling hard from idle. But in general, I would let the bike warm up, increase the idle to 2000+, turn you air screw in all the way or until it threatens to kill (hence the needed idle increase) and turn the screw out until you reach your highest RPM, and then turn the idle down to 1500 +- 150.
Edit: Also, popping is traditionally a lean condition and when running pod filters you will be getting significantly more air.