Early issue Did Not have a Groove for the "O" Ring and the Later ones Did.
It can be said that a SMALL AMOUNT of air May pass by the the Air Screw and no doubt that is why HONDA Added the "O" ring later.
The Throttle Stop Screw has a Rounded End. "uses the longer spring" .................lm
Dr. Frankenstein wrote:That raises an interesting question: it's a PW22 carb, and the air screw is the one with the rounded-off tip, with a spring in the hole.
The diagram that I have shows a little o-ring for it, but yes, I agree that some use one and some don't. No pic yet, but that does give me a pause for thought...Does this carb need that o-ring…?