Cleaning the Valves
The valves must be disassembled for cleaning. First loosen both string set screws and remove the string, as already outlined. Then proceed as outlined for oiling. After the rotor has been loosened and the back head has been forced out, remove the stop arm retaining screw and take out the valve rotor. See Fig. 29 for picture of the valve rotor.
Remember particularly how the valve back head is removed, as described above under "Oiling the Bearings of the Rotary Valve." Many players have damaged their back head bearing by trying to pry it out by inserting a thin piece of metal between the casing and the back head, or by trying to lift the back head by catching hold of the shoulder of the back head bearing with a pair of pliers. Do it the easy, professional way; don't be a dub and ruin your valves.
If the valve rotor has become corroded and stuck in the casing, try a little penetrating oil on the back side of the valve between the back head bearing and the short shaft bearing. Also, you may have to take out the stop arm retaining screw and remove the stop arm and hub from the long rotor shaft bearing, so you can apply gasoline or penetrating oil between the long shaft bearing and the front head bearing. Then be sure to put back the stop arm retaining screw so that you can tap this screw head and not the end of the long shaft. To top the end of the long rotor shaft directly may "jimmy" the threads inside the shaft.
DON'T EVER TRY TO LOOSEN THE VALVE BY FORCING DOWN THE VALVE KEY. If the string doesn't break first, the key lever is liable to be broken off.
Once the rotor is out, wipe out the valve casing and clean the rotor. Also wipe clean the back head, valve cap, stop arm, and retaining screw. If corrosion resists ordinary wiping, use soap and hot water or a mild metal polish, such as the metal polish you use on the outside of silver and unlacquered brass or nickel silver instruments. Be careful not to damage the bearings by vigorous scouring. Be sure to remove all traces of metal polish by thoroughly washing in hot water. Dry all parts carefully, especially the casing and rotor.
Oil the bearings before assembling the valves. Use a high grade fine machine oil, such as valve oil. Place a drop inside the back bearing and a drop inside the front bearing; also a drop on each of the shaft bearings. On the horn, the rotor is suspended between these two bearings, and the sidewall of the rotor does not touch the sidewall of the casing, by about .0015" (one and one-half thousandths of an inch), or half the diameter of a human hair. For this reason no oil should be put on the rotor, but only on the bearings. However, on many other rotary valves the rotor itself acts as a bearing and contacts the sidewall of the casing, and oil must be placed on the rotor to relieve friction. Be as sparing with the oil as possible, as too much oil slows up action and is almost as bad as not enough oil.
Be careful when you assemble the rotary valve. The rotors arc marked No. 1, No. 2, etc., usually on the back end. The back valve head and the valve cap are also similarly numbered. Be sure you assemble all of the No. 1 parts in the No. 1 casing and all of the No. 2 parts in No. 2 casing, etc.
After putting the rotor in the casing and seating the valve back head, turn the rotor so the air column by-passes through the valve and so the valve slides are closed. Do this before you put the stop arm on. To determine how to do this, refer to the drawings in Fig. 28. In view A, note a mark on shoulder of back head bearing, (3). Also note marks (4) and (5) on the end of the short shaft. Set the rotor so mark (4) is directly below mark (3). This puts marks (4) and (5) in the position of the hands of a clock when it is nine o'clock.
When the rotor is in this position, slide the stop arm hub over the long shaft. Note the end of this shaft is square on three sides but is round on the fourth side. This shape makes it impossible to put the hub on the shaft except in one position. This position puts the stop arm in between the two corks against which they stop IF the rotor is set properly, as described above. If the rotor is not set properly, when the stop arm hub goes over the end of the long shaft, the stop arm itself may fall outside the arc within the cork stops. The valve of course will not work in this position.
Once the rotor has been set as shown in view A and the stop arm hub slipped over the long shaft, the retaining screw should be screwed in and the valve cap screwed on. It remains only to install the string and adjust the height of the valve keys, as previously outlined.