I got this Rockwell OHV four stroke going (with virtually nil throttle control), by swapping the carby out of an identical Wesco mower with smoky engine.
When cold, rev level is ok but rises a bit high once used for a few minutes. I tried turning in the outer screw clockwise (second picture showing front view of carby) which worked on my V40 Victa OHV motor, but makes no difference with this. Could there be an air leak or linkage fault? Third pic shows linkages behind carburettor.

Hi MF,
Get it started, mow the footpath and then lurn it off and leave it there........
problem solvered.
speedy

That is a bit harsh speedy, those chondas aren't really that bad, at least it has the outer airfilter cover, most I end up with are missing the cover.
MF, has somebody messed with the governor, although I doubt that because that usually makes them run flat out. The most likely issue is the governor springs have a bit much tension on them and that is a real juggling act to get it balanced out, but that is where the problem will be.

G'day Mf and Speedy,

Sometimes on the governor linkage you can move springs into a better position to stop the motor revving too high
but other times I just adjust the governor arm ,undo the bolt once you have scribed a line so you can see how much
you have adjusted the position from the original position then tighten the bolt after you moved the arm.

If you go the wrong way the revs go up.

If there is no mixture adjustment on the carby then I would adjust the governor arm.

Cheers
Max.

G'day NormK, maxwestern and speedy,
appreciate the suggestions, I have more of an idea what to try next..
Speedy, good one, but after treating the superficial rust and painting it -albeit roughly, it's not a bad mower for a small yard. It's solid enough and has good blades, the motor starts easily and has been serviced.
If I can't get something for it, I'd rather keep it as a going over mower as it's light to push around.