Originally Posted by
Miele Man
Are you positive that it's the shifter and not a worn 4th gear cog?
Good point, and just about the best case you can hope for.
Originally Posted by
Trsnrtr
9 speed Shimano bar ends are notorious for cracking in the bezel which causes shifting problems as the internal parts begin to slip past each other instead of engaging. It starts off subtly like the derailleur needs adjustment but worsens quickly. Look for a crack in the plastic bezel. Never heard of anyone being able to rebuild one.
Those plastic parts will make an interesting sight when you open up a badly worn bar end shifter. One look inside and I was sourcing a new shifter.
It might be possible to rebuild the shifter, if you could find parts. AFAIK Shimano doesn't make them or sell them separately. If you're so inclined, you might buy a new shifter, measure everything very precisely, and save the resulting design to "additively manufacture" new parts as needed a few years down the road.