I've had this saw for decades. Last year it would not crank and cylinder pressure gauge indicated bad rings or worn cylinder/piston wall. I replaced cylinder head (with piston and new rings) and it fired right up with full choke set. However, when I press the throttle trigger, it releases choke and motor dies. Gas is less than 2 months old and has premium 2 cycle oil added. I replaced old carburetor with new one and the problem repeats. I adjusted H and L carburetor adjustments by 1.5 turns out from stop for a starting position, but the problem repeats. My next and only step is to replace fuel filter. I am at my whit's end. And suggestions???????