Weed Eater mower with 4.75 B&S engine won't start after sitting up for 3 years. Drained old gas, removed and cleaned carb,. It will run when primed through the spark plug hole, but only burning the primer fuel. All passage ways in carb. was cleaned and air blown. Carb bowl and float works properly.Bowl drain plug cleaned and blown. Gas flows through carb when manually pressure pumped. What did I miss?