From no start to questioning your crank seals is a big jump.
I would clean the carb about a dozen times and make sure the reed valves are perfect before diving deeper into the engine.
While the carb is off, hold your hand over the intake manifold, turn the engine over slow and see if you have any intake vacuum.
Make sure your oil injection lines are all good or properly obsoleted.
If your intake vacuum pressure is low, it could just as easily be gummed up and stuck piston rings.