White Spark??... Do a proper spark test using a tester whereas you can adjust the gap. ON that model engine, set the gap to 1/4". You should get a strong blue lightning like flame... a real snap!
The fact that you can get the engine running by priming it with fuel indicate that fuel is not flowing through the carburetor... BUT... then again, you state that the engine runs fine after you prime it which indicates that fuel is indeed flowing through the carburetor..... sorta contradictory and confusing there. At any rate, do the following adjustment setup, then get back to us.
(Carburetor Adjustment - Single S/S Adjustable Needle Valve)
(J. Reeves)
Initial setting is: Slow speed = seat gently, then open 1-1/2 turns.
Start engine and set the rpms to where it just stays running. In segments of 1/8 turns, start to turn the S/S needle valve in. Wait a few seconds for the engine to respond. As you turn the valve in, the rpms will increase. Lower the rpms again to where the engine will just stay running.
Eventually you'll hit the point where the engine wants to die out or it will spit back (sounds like a mild backfire). At that point, back out the valve 1/4 turn. Within that 1/4 turn, you'll find the smoothest slow speed setting.
When you have finished the above adjustment, you will have no reason to move them again unless the carburetor fouls/gums up from sitting, in which case you would be required to remove, clean, and rebuild the carburetor anyway.