Novarossi carburetor problems?
 

I've had 2 carbs lock up on me as of late. Middle of last summer, on my 528, the sliding portion of the carb seized up and wouldn't move. I had a buddy have the same thing happen to his 528 later in the season. Yesterday, on my 21P5X, the same thing happened again. They are plastic carbs, and I haven't had any of the carbs apart yet. I can't speak for my buddy's engine, but I know none of mine have ever exceeded a temp of 270.

Anyone else have these issues? Any resolution?