Originally Posted by 155lee

Inbetween the air entrance and the fuel metering head is a tube with 2 screws,inside there's a Allen or flat headed adjustment screw for pushing down or raising up the flap,more than likely seized though so wd40 it to start with.
I'm guessing that it won't start due to no air which says to me the system us airtight as if the flap is closed and sealed then if there was an air leak that would allow air into the intake and the engine would fire,you pushing the flap down is allowing the air in so I'd say try adjusting the screw.
Pretty sure you set the gap between the flap and filter housing with a feeler gauge,maybe have to google the recommended gap?