Engine Just Cuts Under Load, idles and revs fine

[Blue_Smartie]

Having a problem with my 4 Stroke 150cc dirtbike
Just got anew carb (the old one was stuffed), 26MM Mikuni Copy (looks exactly the same inside and out) and no matter what i do i cant get it to run properly under load, i can have it idle for as long as i want, it will rev up to redline fine but as soon as i pop it into gear and go to take off it just cuts out i've tried different needle and idle screw settings (i dont realy know what i'm doing here, but i do know what each thing does) i've replaced the spark plug and i'm now fresh out of ideas, i just really cannot figure it out!
Strange thing is though, when i first put the carby on, i did 2 laps around the whole block and the bike was running smooth as, and since then i've mabnaged to have it running smooth for one lap around the blaock (probably a total of 600M per lap) and that was it
I managed to get it running it 2mm of throttle above idle all about 400M cruising extremely slowly but anything above that it just cut out.
Any advice would be greately appreciated, i would love to have it running by the weekend!
Regards
Chris

[No-Fear]

check the needles on it, check the clip position, even try your old needles to see if it will run.

[gazza2003au]

sounds to me like your piston,valves,cam etc are all working as normal i would be looking at either the gearbox or wheel bearings def not ur carby,spark plug etc... as the motor starts and runs fine could even be the brakes locking up?

[Dilox-125cc]

That sounds identicle to my problem i found out it was the brakes locking up see if that is the problem.
Peace dylan

[Dirt Bikez & Pocket B]

i had a problem like that could be the engine pressure hose is blocked. :shock: