not the tranny, this part: http://www.clermontmotorsports.com/s.../Detail?no=125

The little spring control the about of tension on an arm, when the transmisson spins fast enough, the arm is forced out to grab the second gear spur, it is hit and miss with them, i have 2 xp's , 1 has shifted fine from day one and one had to be changed, easy fix for $3.50. Sorry bro, you can try to fool with the setting some more but i wouldnt break the transmission down to try to fix it, your better off replacing it.