this is a link where you can buy the NT carburetor.
which is on all of the chinese motors except the grubee gt5.
grubee carburetors brings too rich fuel.
I had the grubee gt5 and first it was running ok then later on it gets sluggish and hard to start and engine won't idle. and top speed got lower. and as soon as i changed my carb to NT carburetor. It was running very good.
you will find out as you ride your engine for more time.