Loving this build, it looks great! I'm not the expert, it may be fine, but if you have tuning problems the first thing I would suspect would be the tube from the mouth of the carburetor to the air filter. It would probably stand to benefit from a bigger intake tract or some sort of "dead air" space like what an airbox would provide. Again, it might run fine as is and I realize an airbox isn't really much of an option, but if it didn't run right that's the first area I'd suspect.
85 Tri-Zinger 60
85 ATC250SX
86 ATC250SX
87 ATC250SX
02 XR650L conversion
84 ATC 480R