tri-z and yz 250 ?

im guessing the engine on the tri-z 250 is not the same as a yz 250 but maybe you guys can still help.. the engine was just rebuilt and theres maybe 10 hours on it.. but every once in a while when its warming up, just letting sit and idle.. it will start to rev up and stay there, in high rpms. The kill switch wont work when it is like this the only way to get it to stop is to turn the choke on and let it die out :/ any ideas ?

ah thanks i just heard that again from someone else so im thinking you guys are right.