my nx250 runs fine until I accelerate quickly and then it dies. i've cleaned the carb twice and no matter where i set the pilot screw it still does this. the accelerator pump works but after i open the throttle to a certain point, it stops moving. i think that's what it is but it squirts gas out so idk.
Logan: Bit of a waste of fuel to test it this way but try it again and as the engine starts to die unscrew or flip open the fuel tank cap, if it starts to respond it's not venting thru the fuel tank cap. The vent may be partially clogged, you use more fuel on accelerating, the fuel can't flow properly so you sorta run out of fuel to the carb(s). Check that out.
Another suggestion – water in the gas.
A couple of drops of water in the float bowl can create problems.
Water is heavier than gasoline.
It accumulates and sits at the bottom the the floarbowl under the gas (it looks like a jelly fish floating around).
Upon heavy acceleration, the strong vacuum of the engine lifts the water enough to restrict the jet openings.
When you let off the gas, the water drops back down to the bottom of the floatbowl.
Drain the carburetor into a clean cup to see what comes out.
Check your floats . It could very well be that your float bowl is emptying faster than it can fill .
On that same note , if your float needle is sticky or clogged , it can slow fuel delivery .
When opening the throttle causes the bike to die , that means a flood of air with no gas . You have some sort of fuel starvation .