I tried with the barrels and with the screws, but even when i try to shift from the small cog to the middle cog, (1 to 2), the chain does not shift. When i shift to 3 though, the chain switches to the middle cog instead of the large cog. When i shift back down to 2, it stays on the middle cog, and when i shift down to 1, it moves down to the small cog. Any ideas?