I'm building a bike:

http://www.bikeforums.net/showthread.php?626894

My last step here is getting the thumb shifters. I had a SunTour Mighty Shifter on the right as the RD shifter, and I was temporarily using the left Suntour stem shifter for the FD.



It worked fine, but I wanted matching thumbshifters.

The other day I bought a set of SunTour Power Shifters off the Ebay, similar to these:




They're pretty obviously paired- they're mirror images of each other. They both appear to turn fine and ratchet well in the opposite direction.

I put them on the bike, installed them as the single shifter was installed, with the screw side in, clamp side out- new cable. The shifter switched across all gears, but it snapped right back through the ratchet to the smallest gear- as if there was no resistance against the derailleur spring tension. The front one worked fine. So I thought I might have them swapped around- so I swapped them so that the screw is outward and the band inward and the left is now the right... Now the RD works fine, but the FD snaps right to the smallest chainring- same thing it did on the other side.

I compared the ratcheting direction with the ratcheting SunTour shifters on my old Stumpjumper- on that one the left ratchets left and the right ratchets right. On these, they both ratchet to the left.

Is the shifter broken or is it assembled backwards or something?