Smoke out of carb

If you have a compression tester like the Milton I have, the hose is a quick connect and can be hooked up to an air compressor. You can thread it into the spark plug hole and pressurize a cylinder and listen for where air hisses out. Make sure the piston is at the bottom and both valves are closed. The hissing air will clue you as to bad valves, bad rings, etc.