ORIGINAL: Bob Pastorello
I have limited experience with doing this, but the ONE failure of the screw to remain tight did it for me. My understanding is that not all screws are swaged behind that shaft where the threads are protruding, but I could be incorrect. I've been told that ALL of those that are held by screws in brass shafts ARE swaged.
So yes, I would recommend a new shaft and screw, for sure.
Bob, I 100% agree with you. If you need to take the screw out of the shaft out then have a new shaft ready to put back in with a new screw. Then use red Loctite. Be sure the disk is seated properly before the Loctite sets up. My experience is that all Walbro carburetors have a swagged screw. What I've found is when the screw is removed the swag will often cause the shaft to crack through the thin threaded area. This may not be readily apparent unless you use a magnifying glass and a bright light. At a minimum you will severely weaken the shaft due to brass removal. When your engine is running and it ingests the screw it is the kiss of death for the engine. Been there done that. Same goes for the choke shaft screw.