I would make sure that the throttle plates are sycronized, alot of the time when people redo the carbs they will not adjust the throttle plate, this causes some cylinders to get more throttle advance than tha others, the engine will troll rough, cough spit and die at idle. take the front cover off of the carbs, loosen the throttle plate screws, then flick each throttle plate and make sure it is shutting all the way, once you get them all the way shut tighten the throttle plate screws and recheck that all of them are are shut all the way down at idle.
Basically if the plates are set wrong the top two cylinders can be trying to idle at a different speed than the midlle two and so on, they have to be all exacty the same for the motor to run right. After you get them adjusted open the throttle all the way up and make sure they are all in the same position at WOT. This is one of the most overlooked steps in two stroke carb overhaul, I bet 60-75% of the motors on the water today are wrong.