Rotary valve 4 stroke inlet/exhaust port timing may exhibit similarities with two stroke I/E timing.
Two Stroke Tuners Manual
By G. Jenningshttp://www.vintagesleds.com/library/man ... ndbook.pdf
"The advantage of a rotary valve is that it enables the two-stroke engine's intake timing to be asymmetrical which is not possible with two-stroke piston port type engines. The two-stroke piston port type engine's intake timing opens and closes before and after top dead center at the same crank angle making it symmetrical whereas the rotary valve allows the opening to begin earlier and close earlier.
Rotary valve engines can be tailored to deliver power over a wider speed range or higher power over a narrower speed range than either piston port or reed valve engine. Where a portion of the rotary-valve is a portion of the crankcase itself it is particularly important that no wear is allowed to take place."
Make note of Uniflow Scavenged Engine timing diagram.
Thread Belatti kindly researched and specifically recommended:
"Valve timing Intake open 20° BBDC 520° close 60° ABDC 240°
Duration 440° (this is not a mistake)
Maximum port area at 20° ATDC
Exhaust open 40° BBDC 500° close 60° ATDC 60°
Maximum port area at TDC 0°
Overlap 260° (this is not a mistake)"
Well worth your time to study previous thread.
Also G Jennings section on ignition timing.
OT - Interesting saying 'Axe to grind' - here we answer that with the folk wisdom 'It's easy to hang a corpse' and of course the modern equivalent ... 'It is what it is.'