@GeorgeSanJose--Two stroke lawnmower engines are easy engines to replace the rings. I used to do a lot of mowing for people when I was in high school. We had a LawnBoy mower with a 2 stroke engine. The cylinder walls were tapered, soa ring compressor was not needed to put the piston back into the cylinder after replacing the rings. At the end of a season, I would buy a set of rings, a new needle and seat for the carburetor, new points and condenser, a complete gasket set and a new Champion J-8 spark plug. After removing the cylinder from the crankcase, I would pull out the piston, rough up the cylinder wall with some crocus paper, scrape the carbon off the piston and install the new rings, rebuild the carburetor, reassemble the engine, install the points and condenser, put in the spark plug and it was good to go for another season. I chickened out on my 4 stroke lawnmower. When the engine puffed oil smoke and lost power, I just installed a new short block. Not only would the valves have to be ground, but a ring compressor is needed to get the piston back into the cylinder.