I was told the saws require a stiffer diaphragm (carb). The current one is causing the saws to load up with too much fuel during idle.
I expect ( and I am not a saw expert )once the saw gets up to working tempature it causes the diaphragm to soften and pump more fuel than is required at idle. Hence it worked good when cold. I do know My saw will be receiving an updated stiffer diaphragm, the fix to my hesitation issue.
I still can't understand why some saws work fine and the two I got had problems, even after the carberators where replaced. Perhaps it is me, and my cutting style, I tend to not cut as much air as others I see and hear cutting.