Ok, one more tweak junkie to chime in on these needles. I have them in with .040" shims and it seems about right. Without the shims the flat spot remained at about 3500rpm. I have the Freak, 160 mains, 42 pilots, air screws at 3 turns, and Sceptres. I also drilled the small vacuum signal hole at the base of the slide out to .125" and cut 3 coils off the slide springs. Throttle response is solid.
I did some measuring of the stock needles and the Tbird needles and found something interesting. While the Tbird needle is actually .001" smaller at the top, both needles start their taper at nearly the same point. Obvously the Tbird needle tapers much faster, but the transition to the taper may not have been reached yet when the bike is in that 3000-4000rpm range. This theory seems to make sense to me as to why my lean flat spot remained until I added shims.
Any opinions?
