These two gears he's talking about are clearly visible in photo
100_2259.

You need to change the small input and output gears on the pair
of big gears so that they are both on the same large gear.

Also see pic 100_2252 which shows the "a" and "b" gears both
meshing with the 127 tooth gear. That's not how yours are set
up...
--Glenn Lyford