Old o-rings under the float valve seat? Often, when cleaning the carbs, the old o-ring becomes damaged (sometimes just from carb cleaner) and will then leak fuel, causing overflow - always replace these o-rings when cleaning the carbs.
'01 660 Raptor, Burgard +2+1 arms, YFZ Shocks, LSR anti-vibe, CTR pipe, jetted, K&N
'01 Polaris Scrambler 400, K&N
'02 Honda 400ex, Big Gun pipe, jetted, K&N, Lonestar +2 A-arms, Lonestar anti-vibe
'02 Honda 400ex, DiamondJ +3 A-arm widener, Lonestar anti-vibe