The decomp valve is for your benefit only...reduces effort to start but doesn't really help the saw any. Sounds like you are doing it right...but there may be something off with the saw. Mine takes about 1/3 of a pull when warm to fire up. You might have a fuel issue (bad line, clogged tank vent) or weak spark that's making it hard to start. Next time after you run it for a while, shut it off, open and close the gas cap and try again. If still hard, pull the plug and check to see if there's any noticable fuel. Check for spark too. If you have spark but no fuel, then might be time to start trouble-shooting the carb and/or fuel lines.