Yes you are right. The float valve is there to cut off the fuel supply when it reaches a certain level. If they are not shutting off the flow it could be one of two things;
1) The float valve seat has gone. It takes very little to break the seal of the float valve (minimal wear, speck of dirt, strand of fluff etc). These are cheap and easy to replace.
2) The float height is set wrongly. This can be done accidentally without realising. One possible way to check if it is the float levels is to see if the problem occurs on both the side stand and centre stands.
It is possible to remove the carb bowls when fitted to the bike but there isn’t much room to work in. If they are fitted with cross head screws be careful you don’t round them off
