Model Fl1500 Feather Lite Pull Cord Jerks And Is Hard To Pull However When Spark Plug Is Out Pull Cord Is Easy

When the plug is out there is no compression at all so the engine can freely spin. Many very light weedeaters jerk around when you try to start them. I usually hold mine to the ground with my left knee and pull the rope with my right hand.

I believe you are correct ball.