I picked up a 'tag 92 recently and cleaned out the fuel tank and pick up. It started fine, but would quit after a few minutes of running. At first I thought it was old gas (about 30 days old), but when the tank was drained and fresh gas applied - same problem. It would run about 4 or 5 minutes and quit. I changed plugs, same deal. I finally decided to check compression. Found it! Cold, compression was excellent. Hot - virtually none! If I let sit 10 minutes, great compression again. Ok, so it needs new rings. Only one problem - when I pulled the cylinder, guess what I found - NO RINGS!
Seems this engine was dis-assembled years ago, and was put back together with no rings!
The grooves were in good shape, and they were full of carbon, so this engine was run a while this way. I thought of re-assembling it as-is just to make people try and decide what was wrong with it, but just ended up installing the new rings after cleaning off the carbon. The engine runs fine now! You never know what you will find!