rcpilot
the piston in all 3 of my ryobi's goes past the bottom of the port durring the piston stroke .the theory is that the exhaust gas hit this edge of the port and creates an eddy of exhaust gas which disturbs the flow out of the engine and partially blocks the port to flow.
I dont think turning the jug shorter will help because of the transfer port timing if you shorten the jug then you move the ports lower delaying transfer port opening and shortening there duration they are open, you will get higher compresion but less fuel\air mix in the cylinder,also these ports aid in exhaust gas scavenging so delaying their opening also efects the way the exhaust is removed from the cylinder so it may in fact have the reverse effect
I have just finished my second cutting sesion on my exhaust port now it has 147degrees of duration will run it today and post the results later.
I think aero nut hit it on the head with the duration of the exhaust port I didnt gain as much top end as I would have prefered with my first cutting sesion but the engine is way more powerful and responsive to throttle input than it was ,we'll see in a little while