Remove the 4 screws that retain the cylinder. Carefully pull the cylinder up from the case. You may need to use a very slight twisting motion for the cylinder to break loose from the gasket. Try not to tear the gasket, and do not press on the piston ring during the cylinder removal. Once the cylinder has been removed use a paper towel to block off the open case top. Then view the piston and ring. If the ring has stiuck it will have done so on the exhaust port side of the piston. Easy to see because it will be flush with the side of the piston while it will be sticking out from the opposite side of the piston. If it appears struck, apply light pressure to the side sticking out. Any resistance of the ring to pop out the other side means there is a carbon build up around the ring and groove. Carefully remove the ring without bending it upwards. They are brittle and will break easily if forced to bend. Carefully clean the top of the ring groove, the top of the ring, using an exacto knife, and the back of the ring using an exacto knife. Flush debris away with a can of WD 40 and a spray tube. The best tool you can have to clean the ring groove is a broken ring but I don't expect you'll have one of those around. Be creative but don't gouge the ring land (top or bottom) with a tool while cleaning away carbon.

Reassemble by first getting everything wet on the piston and inside the cylinder with some ore mix oil. Be sure to get some on the roller bearings at the carnk and the piston wrist pin. If you have the tools, the torque spec for the head screws is 35-40 inch pounds. If not just slightly more than snug tight is close. Don't white knuckle the hex wrench because you'll strip the threads out of the case. Tighten the screws like you would the lug nuts on a car tire. Cross pattern.