The clip move should help some.
I experienced a similar problem when putting on a freeer flowing air filter on my GY-5 200.
There is also a fuel screw on my carb. In most cases people don't need to mess with them. (Although RPM said he does adjust them when setting up new bikes for customers).
Here is a picture of it on a Lifan:
http://www.chinariders.net/gallery2/...g2_itemId=1092
(I don't know what engine you have so the screw may be in a different location)
To get it to run richer start backing out the screw. (counter-clockwise if you are looking directly at the head). If there isn't a factory marker line then you may want to use a sharpie and mark the original setting.
Start backing it out about a quarter turn at a time. Go ride around the block and then adjust again if needed. I had to go about 1and a quarter turns out to smooth out the sputtering.