From memory the float height by Keihin spec on the shallow bowl models is 6.5mm. Given the angle the carb sits in the chassis though I have found setting it to 7.5mm works a bit better and haven't had any starvation issues.
The old lean her over 45 degrees and wait for the fuel to come out the overflows gives a decent indication too.
Thread here:
http://www.gasgasrider.org/forum/showthread.php?t=11886