@vickytulla bro, little help if you are still visiting here.
Throttle twists fine when bike is off but once you fire up the engine, throttle goes heavy like something is pulling down the slide needle inside the carb. I am done troubleshooting this carb which i believe is Mikuni VM20.
Kindly suggest some other replacement carb which suits 150cc and can fit on GR150's intake manifold.