RE: another darn ryobi post (ryobi performance modification, analysis and comparison)
You can't change the intake port timing on a reed valve engine. The reed opens whenever the pressure differential is favorable.
The transfer ports I didn't change, and still got very good results. The transfer ports are difficult to work on. If you modify them, you must be sure to maintain the original exit angle of the ports, and make sure the ports are identical to each other in timing and angles. Unless I am working on an all out effort engine, I just leave them stock. The exhaust timing is more important because it is often set very mild on these engines.
AV8TOR