This mower was given to me. It sat for 4 yrs. with gas still in it and was never started during this time. I have cleaned tank, carb., replaced spark plug. The only way it will even start is by putting or spraying carb. cleaner or gasoline directly into plug port or carb. As soon as it burns off, approx. 4 sec., it dies. It is starving for gas but can not see any adjustments on carb. Can anyone help?