In December I got a new John Packers Bb Cornet and it was fine to start with. But recently the valves have been sticking, especially the 1st and 2nd ones. Even when I put valve oil on them they stick. It's really starting to annoy me, is there any else I can do to prevent this?
If the valves continue to stick after being oiled, then it's time to clean your horn. Remove all the valves (making sure to keep them in order so you don't put them back in the wrong casings) as well as the slides. Fill a sink with warm (not hot) water with liquid dish soap. Wash all the parts gently with a soft clean cloth. There are special brushes available at music stores for cleaning the insides of slides. After cleaning, pat everything dry, apply fresh grease and oil, and reassemble.
