I have been following this thread and have test run a Ryobi intended for a Sparrow hawk (50CC) or 2.00 FS size.
I used a bowman ring ,150deg exhaust timing, 12mm Walbro, replaced the cylinder gasket with a thin one , gutted the muffler and used a cylinder with slots, as I have never seen one here in Australia without slots.
I got 7400 from it even though it has not developed that snap you get when the compression is good and you flip it over.
My question is does the compression get better as you run it in and how long does it take.
I tested the ring in the bore and there is little to no gap but I expected more compression than I got.
I took the ring off the piston and reduced the thickness a bit on some fine wet and dry paper as it was just a bit thicker than the original and I will test it again.
I hoped to get 7700 from it which would fly the Sparrow hawk with about 16 lb of thrust.
Any suggestions for developing more compression.