01 Phaser Engine issue

assuming that the carbs are clean, check the output of the stator. you will need access to a service manual that will give info as to what ohms at a given temperature across specific wires. a good dealer should share this info. easy check, except most readings are spec'd at 68*F. so you need a warm spot for troubleshooting.

stators are a funny item. things will work just fine until certain conditions are met or exceeded, and then they will act up. usually a small frayin the windings.your situation sounds like a stator issue, although rare on that sled. one other thing to consider would be a rodent nest in the pipe or airbox. depending on where you live and where the sled was stored, these are a couple of areas to rule out. who serviced the carbs? try flipping the choke lever on when the sled starts acting up to see if there is a running difference.