This isn't per book as I don't have one. I just waited until before starting it one cool morning. There's a metal ring screwed on the outside of the plastic part of the choke. I loosened the screws on the ring a little and turned the plastic piece until the choke snapped closed. Then I tightened the screws and ran with it. The electric part is supposed to warm up a coil of metal in the choke and pull it back open as it warms up. Mine is still hard to start though, even with a working choke.