JB,
Every carb is going to be different, even brand new carbs, so it is hard to say what percentage of a turn to richen. That is one reason I always adjust the H needle to maximum RPM. The other reason to adjust to maximum RPM is just like I told to TL in his post, the 2 cycle "power band" is reached at this point, giving you maximum horsepower out of the engine. My personal trimmer is an Echo, and I've been running this setting on it for the past 11 years, not to mention my Sthil chain saws and Ryobi blower. Customer's just love to hear their equipment "scream" like they have a new engine with power like it never had before.
