I'am 99% sure your problem is water in the carb, its a b*****d if you strip the carb again, look in the front (engine side) you will see a tiny hole that leads to the emulsion tube, this is blocked the only way to clear it is with an air line ! Aerosols ect.. won't touch it !!! This happend on my lads beta and his lem mx bike (same carb) i did all the things you did cleaned the carb over and over. In the end i toke the carb to work and shoved the air line in every orifice and out popped some water !!!!!! In the future if it happens when your out riding try putting the choke on and drive it along, this sometimes drags it out but not very often hope this helps !