How do you guys go about modifying the exhuast duration? I don't know much about modding two strokes, I assume you are opening up the top of the port to allow it to exhaust longer?
Have you run the engine and have you decided on a muffler. What exhaust duration are you designing for? The two issues are sort of interrelated.
Bill
Many years ago the motorcycle racers would remove material from the piston to modify exhaust duration. After looking it appears that 1mm could be removed between the top ring land and the top of the piston. Over the years my degree wheel has disappeared. Will make another one to check the difference in duration.
Flipflop reported the exhaust timing to be 122* in post 44. Improvised a test and it appears that removing 1mm would gain about 7* duration.
Whatever you decide you should test before and after so you will know when you went too far.