Quoted from paulace:On that same site that @curriedog mentioned, there's a nice photo of a pivot that often gets gummed up and won't let it decrement cleanly. Make sure that part is able to move freely - clean with mineral spirits or alcohol until it does, then maybe a drop of light oil.
[quoted image]
That's great advise, referring to the shoulder bolt in the photo... often times you'll find hardened lube or other substance that requires a little bit of work, namely unscrewing the nut from the back, then gently loosening the bolt just a bit (no need to untighten too much as those bolts tend to break if worked hard) in order to work some degreaser behind the bolt, followed by a drop of fine oil... re-tighten a bit but don't over-do it. I leave shoulder bolts just a smidge loose on the frame, allowing free movement of lever arms as intended for consistent operation. Don't forget to re-attach the nut to the back of the bolt.