i got a kx60 that i am fixing for a friend, it has a 190 main in it with a pro circuit pipe, it will fire up and go for about 200 feet then just start to sputter and die out. im thinking maybe its something to do with jetting?
i had a kx60, sold it last year, the thing was a PITA to jet but once you get it right, they rip for a little bike like that. It popped wheelies with me on it.