Hmm, I took a look at the code, but see no check to stop the motors when in a balance of the sensors (if they were moving).

Maybe this will help:

Code:
greater: 'greater routine
b2 = b0 - b1 'find the difference
if b2 > 10 then cw 'is it within the range? if not go to clockwise/ solar panel facing west
low PORTB.0 'pin portb.0 low /stopping the solar panel for moving
low PORTB.1 'pin portb.1 low / stopping the solar panel for moving
goto start 'if it is in the range,do it again

lesser: 'lesser routine
b2 = b1 - b0 'find the difference
if b2 > 10 then ccw 'is it within the range? if not got counter clockwise/solar panel facing east
low PORTB.0 'pin portb.0 low /stopping the solar panel for moving
low PORTB.1 'pin portb.1 low / stopping the solar panel for moving
goto start 'if it is in the range, do it again
This is an idea, not tested.

Ioannis