Ur:

The cylinder liner in a K&B 40 engine is a light push fit when all the parts are clean, but they tend to become locked in place after a few hours running time.

Practice with the engine that has the broken ring. Pull the head and back plate off, use a hardwood stick and try to push the liner up and out - you can push against the bottom of the cylinder liner on the side away from the exhaust, under the bypass ports, inside the crank case.

If you can't move the liner then as Paul said, heat will be needed. After taking the front cover off also put the crank case with the liner, piston and rod still inside, into your oven at 275-300F for 30 minutes and try again. If either liner will not come out just stop, switch the good ring and piston only. Reassemble the engine and enjoy it. The ring will have to reseat, but if you force the liners out you're likely to do more damage.

Bill.