in the freestyle areans that are indoors the guys arent allowed to start their bikes till like 45 seconds before they go out and do their run, while there putting it the choke is on, and notice how they smoke alot on it ?, then before they go off they hit the choke, rev it up, clean it out and boom, also alot of the guys do a hands on of the fuel valve to be certain they dont pull a "chicken" i dont want to drop names on who i know in the world of freestyle mx but this is what i was told by some pros, i had to ask too.