Here's what I did to the carb barrel on my Saito 62CL. They're not a great fit, so leakage is a possibility. I turned a notch into the outside edge and fitted an o-ring to positively seal the barrel. Added an M5 nylon screw as I do to any engine that could benefit from speed regulation and adjustment. And I cut down the spraybar so that it feels from about half-way once the nylon screw is in there partially obstructing the bore.
The thread for the nylon screw is done with a taper (first) tap, but not all the way through. This makes the nylon screw a tight fit, so it will stay where you put it without leaking or winding itself out.
Similar to the famous Bob mods to the RC carb.