Mine would be to high, yours should have come with 30/23 uppers and 16/27 lower gears

Mine was a XR B3 and said to be 1.81 but XR only comes with 19/16 uppers, so closest to the 1.81 was most likely 15/19 which would be used for the 1.50 drive ratio

Rotated the upper and counted rotations of both, 10 upper/7.25 lower 10/7.25= 1.379

Believe mine is a 18/25 25/18 = 1.38 making it for a 1.65 drive using upper of 32/27 only one with that ratio

Other lowers are 15/19 = 1.27 , 16/27 = 1.68 , 13/24 = 1.85