Ryobi compression trouble
 

I need some help with a Ryobi conversion to improve compression.
I have been using these for years but I am having trouble with a motor that lost power and performance.
I have tried a new cylinder and bowman ring but it doesn't develop that snap and when hot seems to have none at all.
I have been using a synthetic oil and thought about going back to castrol 2t mineral for a better seal and breaking in.
I used to get 7600 on the ground with a master 18 x 8 but 7300 is about it now.
I gave the barrel a light scrub with wet and dry hoping it would bed the ring in but no joy.
Any ideas or tricks on how to improve this rebuild would be appreciated..

If the ring groove is dirty and filled with old carbon the ring can get stuck, particularly when the piston gets hot.

Maintaining the correct ring gap and a clean groove is important to prevent the ring getting stuck.