Good plan for the future, but if your engine runs the prime out, something is firing that fuel, and good probability it's the plug. So it's a better than even bet the plug isn't why it's only running out the prime. You really should pull the plug and look at the element no matter what. Look to see if the element is mashed down or to one side. If it's clear of the sides and doesn't look broken, test it while it's out. Connect the battery and see if it gives a strong glow. If it passes all the checks, put it back. Tighten firm, but don't go overboard.


You can easily do that by finger choking. Put your thumb over the opening in the carb to plug it tightly and turn the prop a revolution by hand. Watch the delivery tubing while you do it. It should only take a couple of turns until fuel shows up being pulled to the carb. Used engines sometimes have crud in the tank, fuel tubing, or inside the needle valve. Back pumping sometimes pushes the blockage back into the tank. Try to fill the tank from the engine's fuel line. It will at least show you how clear the path is from the carb back. While the line if off the carb, try to pump right into the carb. If it seems blocked, pull the needle completely out and pump again.