Walbro has a couple of different setups -really intended for the weed whackin market
One version has a detent and a spring --
the idea is that you set the choke -to closed -- this engages the detent and the throttle is just off an idle -
when you yank the rope and the engine starts - you hit the throttle trigger - which releases the detent -- allowing the choke to snap open.
the engine then runs -
at least that is the design theory.

My own setup:
remove the detent and reset the spring tension (reduce it) - by letting the tang on the spring unwind 1/2 turn
Now place thumb over choke plate or put a twist lever on the choke and close -hold closed with throttle very slightly open .
flippety flip until engine burps - let go the choke and it runs
OR leave ignition OFF - open throttle somewhat
choke till thumb is wet - release choke - close throttle- add ignition (stay out of prop arc!!!) then flip to start.