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Discussion Starter · #1 ·
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?
 

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Is the spark coming 3/4 inch after TDC or before TDC?
Check your valves carefully.
Are they closing all the way?
Are they closing at the right time? .... fully closed at TDC or just before.

Maybe mark exact TDC with pen on the flywheel and see where your spark pickup sensor is in relation to that position. Is it possible a wrong coil or mounting has been used?.

Kind of a stumper here.
 

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Discussion Starter · #3 ·
At top dead center, both valves are fully closed. IMG_20210407_203637.jpg
and flywheel magnet is 180 degrees away from coil. IMG_20210407_203656.jpg

When flywheel magnet is at coil, piston is a BDC IMG_20210407_203803.jpg
IMG_20210407_203817.jpg

Tonight I will pull the flywheel. Is it possible there are two key seat in the flywheel or on the shaft? If not that, then I will open the case and look at the timing gears. Any other suggestions?
 
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