This is what has worked for me in the past. OS # 8 plug, 20/20 fuel, Hatori 650 pipe,APC 13 x 10 or 12x12 prop.measure 20.3-4 inches from glow plug to first baffle.
After warm up, set high end first ( at least 30secs) to pressurize, then set low end~ 2500rpm. Let the low end stabilize (20-30 secs) after each high rpm run. If it loads up( Rich) turn reg. screw in 1/4 turn at a time. If it is too lean , turn the screw out( counter) again 1/4 turn at a time. After you make any adjustment to the low end make sure you run it up for 20-30secs.

Hope this helps..

B