A common question of new owners of guitars with a Dynamic Vibrato is how to keep the tremolo arm in the tailpiece bar. The tremolo/bridge unit of the Fender jag-stang and most mustangs is a Dynamic Vibrato, so this article applies to both the jag-stang and mustang.
The first thing to know is that the tremolo bar itself does not “snap” or screw into place like the tremolo bar of a stratocaster. The tremolo bar is held in place by pressure from a small allen screw in the tailpiece bar.
The photo below points to the location of this allen screw. Note the location indicated by the blue arrow pointing into the end of the tailpiece bar.
So to hold your tremolo bar in place get the bar in a position you are comfortable with and then snug the screw in the end of the tailpiece using a 4mm (or 5/32″) allen wrench. Don’t over tighten this screw. (see below)
So another very common problem is that the screw in the end of the tailpiece bar will be missing. They fall out very easily.
There are not a lot of options for finding a replacement screw. You may have to buy an entire dynamic vibrato tailpiece that includes the screw. Or another option would be to pull the tailpiece bar off the guitar and take it into your local hardware store looking for a screw that will fit.
[If anyone has found an exact replacement for this screw please let us know the details and we'll add it to this article.]