Have nephew hold end of spark plug wire while you spin the motor. If
he doesn't make a sound or remains standing then work backwards on the
ignition system which sounds like you've been doing.
Otherwise work backwards on your fuel system.
I'd continue down the ignition system first cause you've covered more
ground there. You'd hate to work all the way back to the tank only to
find it's fine and then return to the next step in the ignition system
to discover it was the problem all along. Also, just smell the
carb...if you smell gas...don't fool with the fuel system till you've
eliminated the ignition system.
Here's where I add this is why people buy diesels :) No stupid
ignition system let alone a quirky fuel system to trouble shoot.