You don't say what type of scooter,or if you were using it daily until you got this problem.If you haven't touched any screws on the carb before the fault don't touch them now,they don't move by themselves.There are other things to look at first,pilot jet or slow running jet as they are called looks like a favourite,dirty carb,don't fiddle with the screws unless you have done work,they are factory set.
Rich
September 2011