Snow blower snapper 10301

[chickenkicker]

I have the snapper 10301 snowblower...no manual. does anyone know why the inside pulley(furthest away from auger) on the blower, I've taken apart to replace belts, freely spins? Why does it do this? it make no sense, the larger belt engages, by idler pulley, and hence the auger starts up.

 

[mechanic mark]

Engine