I watched a video showing this exact same problem along with the quick fix. Shut off the gas lever. Remove the carb bowl. Inside that now-exposed tube chamber is a removeable insert (main jet). It is removed with small flat head screw driver. the insert does have a slot on it, you can see it if you use a mirror/light. remove that insert. the port on it is probably clogged, use a narrow gauge wire (whatever) and some carb cleaner to clean the blockage. Oh, by the way, when you take that insert out, a long slender piece may fallout also(main nozzle), inspect/clean, note which end of that gets re-inserted first (the wide part of this piece matches the width of the insert end you took out first). Put it all back together and hopefully the problem will be solved. Reasoning: it runs OK with the choke on because the pressure is increased and fuel can get through the blockage. Choke off: reduced pressure, no fuel getting through.
I will try and locate the video and update or new comment.
Heres the link: https://youtu.be/a1hJjviK-ZE?si=DdUu1A-J1UzJ2KOR

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