You can buy a Mikuni 30mm clone that should perform better, be easier to tune and be easier and cheaper to change jets in. Look up Mikuni 30mm on Amazon and find the one with 12 reviews and 4.5 stars. Its a clone actually but runs good according to reviews.
Uses a 44 mm air filter opening, 30mm flange opening on back and a 48 mm bolt spacing with may or may not be what you have. You can also get them without the built in aluminum flange and you buy a rubber manifold to hold them.
This is not where I got mine but looks identical and cheaper
http://www.pccmotor.com/30mm-mikuni-...-30200250.html
I had to transfer the choke linkage from he PZ27 to the 30mm Mikuni. Can't seem to find the official name for this Mikuni but it appears specifically made for old Honda CRF XR 200-250 or something similar. DOn't believe the picture they show with bolt spacing, they are not measuring accurately, its 48 mm between bolt hole centers, not 50mm.