One of the great things about o-ring seals is they often will remain in good condition despite numerous disassemblies.
Occasionally, though, you find this: an expanded o-ring that can not be reinstalled. Of course, this o-ring needs to be replaced,
but if you're in a jamb and can't get a new one, there's hope. First, remove the o-ring. You will now need a fresh razor blade
and some Super Glue. You're going to fix that dude! Don't count on this as a permanent repair, but if you do a good job it will
be as good as new. Try to get a new one later on anyway.
Cut the o-ring as shown here, but realize the following: Cut on a clean, flat surface; use a very sharp blade; lightly oil the sides of the blade;
do not roll or slide
the blade while cutting; hold the blade perfectly square to the o-ring and press straight down against the work surface.
You should now have a clean, square cut.
Put the o-ring back in place (without stretching it) so you can mark where the excess needs to be cut away.
A dab with a fine tipped white paint stick or a "White-Out" brush works well. Because you will not be able to
fully lay the o-ring in the groove, you will have to estimate somewhat where the cut should be.
Now cut the excess out in the same way you made the first cut. The trick is to have a perfectly square cut.
Place a drop of Super Glue on one end of the o-ring and glue it together. Pay careful attention that the natural lay of the o-ring is
matched and that the ends align perfectly. It is helpful to glue the o-ring together with it place. The groove helps you keep
everything in alignment. Just don't glue it to the groove. Firmly hold the ends together for several seconds. When the bond is secure,
you can wick away wet, excess glue with a piece of paper towel. Don't glue the towel piece to the o-ring.