That part on the blower you are pointing to is to stabilize the mount when it is removed from the tractor. It locks it all together so that it does not move/flex when it is sitting on the ground, removed from the tractor.
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There should be an extra hole near the end of the upper mount bar that you secure to that stud and wing nut on the lower mount.
You unscrew the wingnut (circled in red). You take the upper mount arm and remove the end from the tractor side (orange arrow pointing), swing it down to the stud the wing nut was on and then screw the wingnut back on.
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The Collection, so far: Cub Cadet 100(x2), 125(x2), 123(x2), 70, 71. Adding more when I can find them.
