I,m running a 36mm mikuni and these are my specs. Was dyno'ed by Carl Batey of Caferacer.com.au did story on 500 motor for VMX mag.
Slide 2.5
Jet(needle) P2(188)
Needle P2(188) clip on bottom slot with an additional shim
Pilot 35
Main 230
There are same rough spec's on 38mm on the SR500 forum also
Curly