The most important places to oil on a rotary valve are the bearings. There is a bearing at each end of the rotor. One is located under the valve cap on the front of the Horn (Figure 1), while the other is to be found under the stop arm on the back of the Horn (Figure 2). One or two drops of oil placed on these bearings when needed should keep the valves turning smoothly. If the valves are still sluggish after oiling, it may be necessary to carefully drop some oil down the slide tubes of the sluggish valve. Take the instrument to a qualified repairman for cleaning if oiling does not work.