I purchased a used Sears edger, number 536.797480, this weekend. I bought a new carb because it's cheaper than a rebuild kit. I lapped the valves and installed new spark plug. Engine has good strong blue spark, feels like good compression, is drawing fuel from the carb into combustion chamber, but engine won't start at all, not even a putt-putt. It appears to be a timing issue. Flywheel key is intact. I tried starting fluid directly into the air cleaner, and directly into the cylinder thru the spark plug hole. Also tried putting a bit of gasoline directly into the spark plug hole. When the magnet on the flywheel is aligned with the coil, the piston is still about 3/4" below TDC. I know plug should fire at about 15 degrees BTDC, but what I see seems excessive. It sounds like a timing issue to me. Engine has electronic ignition. Could this be a bad coil? I don't think so because I have spark. Could there be an issue with timing at the crackshaft gear/camshaft gear interface? It doesn't look like anyone has ever opened the engine block. What should I check next?