I tune mine to the 7/8 second pinch, and it seams to be a great start point!

I only let the motor warm up for about 1 min before i get the 7 sec pinch, maybe you are getting the motor to hot before the pinch!?

At any rate who cares if this method isnt working for you, if you can get the motor to run great using your own method, go for it i say use wat works!!