It sounds like the same problem I had. The local Suzuki dealer said that the float was not available seperately and would sell the carb housing with float for $90. I found a new carb on e bay for the same price. However, after buying the carb I found a source for a float. Go to
www.bikebandit.com and look up carb parts for a '92 JR50. It shows the float for about $15. The pivot shaft is peened into place but I'm sure you could remove it. To replace the shaft you could always peen it back, use epoxy or drill/ tap for small retaining screws. Before swapping parts, you may want to experiment with lowering the float level until the problem goes away or it gets too lean.