2T's have one bad flaw in design. If ANY water gets into the fuel system it sits at the lowest point. Usually in the crankcase. You can try removing the sparkplug, and air filter from the carb.
Hold your hand or a rag over the carb tightly, and crank the engine for 15 seconds or so. That will pull any water in the float bowl into the crankcase.
Then remove the rag/hand, and crank over for another 15 seconds or so with the throttle held wide open. This will expel most of the water, and fuel from the case.
Re install everything, and try to start the bike. You may have to hold the throttle open in order to make it start. If it does start it may take 5-10 minutes of poor running to clear.
I have this happen all the time both with my own bikes, and some that come in for repair. 2T's HATE water, and the water knows this.