THROTTLE SNAP BACK TO IDLE
First thing to do is to lubricate both of the cables! It should be free like you think it should be. the cables pick up a little moisture and they start acting wierd and doing just what you say. you could check the carbs too. but I'd bet a dollar to a doughnut hole that it is in your cables. If they are routed right, and have no crushed places...it doesn't leave much else. It's a little bit of a job, but get together with another buddy and chat, turn on the radio, have some refreshments and just spend the time having fun getting it done. It should get you through the summer once you lube and work them free. Of course you could do it the easy way...order new ones from beartoothkawasaki.com lube them an then lube the old ones and have a spare set, should you ever need them...