I bought a reel from a guy and the first time out with it I had problems. Sometimes when I make a cast and turn the handle to lock the spool the thumb bar stays down and I have to raise it with my fingers to get the spool to lock. I asked the seller about it and he says never happened to him. Any way I have never taken a reel apart and dont know much about the insides. What might cause the thumb bar to stick? thanks

Could either be a bad spring, debris inside the reel, or old grease

Depends on What reel. Most of your Pinnacle, Garica Revo's, Lews, Pflueger and BPS models have a plastic (er...excuse me...NYLON) Clutch assembly that has a tendancy to crack or break. This can cause this. Another is simply a worn clutch pawl that is not engaging the ratchet gear fully to make the transisition. This is the most likely. ONe other thing like Tim said is gunked up parts including the area underneath your thumbar on the exterior that get's packed dirt and grease under it that will not allow the thumbar to fully depress impairing the Clutch mechanism from engaging fully,