change your shift point because you went to a 70 tooth spur it change your gear ratios meaning not only dose the motor spin the tires at a differant speed but it dose the same with the trans adjust the shift point about 2 turns (so that it will shift to second) then once you have it shifting adjust the shift point a 1/4 turn at a time until it is close (be sure to bring the motor up to temperature before adjusting)
once you have it close you can leve it there or start adjusting 1/8 turn at a time but remember that if you make it so that it jusat barely shifts under perfect conditions then it will not under less than perfect conditions