I have an older Redmax EB6200 backpack blower. It starts ok when I am at the first customers house. Once the blower warms up, it gets difficult starting it. (outside temp doesn't affect it at all) I have to choke it with the throttle in just the right spot. Then let off the choke and once it catches, feather the choke till its able to go. New fuel filter didn't help. Fuel lines??? Thanks for any suggestions.