The center pedal on many smaller, inexpensive Asian grands does not activate a true sostenuto, but rather a bass sustain similar to that which is found on most vertical pianos. This feature is accomplished by means of a split damper tray with dual pitman dowels, one to lift each section. If this system is not very carefully adjusted, there is a frequent tendency for the pin on the top end of the bass pitman dowel to drop out from the grommet on the underside of the damper tray. This malfunction consequently jams the damper tray into the lifted position, thus raising the dampers off the strings, causing constant sustain. The following regulating procedure will prevent this from occurring. Remove the action from the piano. Loosen the lock-nut and the washer on the top of the middle pedal rod and adjust the cap-nut for a small amount of lost motion between the bass damper tray and the damper levers.   Follow this by loosening the nut/washer on the sustain pedal rod and raising the cap-nut so that the felted notch on the long damper tray just comes into contact with its interface on the bass damper tray.  Tighten both lock-nuts/washers.  Next, the travel of the sustain trap-lever can usually be regulated by means of a stop-screw or capstan which projects from the underside of the keybed and limits the excursion of the lever.  Adjust this capstan so that there is just adequate damper lift, but not so excessive that on hard depression of the sustain pedal the pitman pin can drop out of the damper tray grommet; some of the pitman-pin must remain within the grommet hole at all times.  If there is no capstan or if the stop-screw is inaccessible without removing the trapwork, you can achieve the same result by installing or building up blocking felt on the top surface of the lever, which will then contact the keybed.  (Hammer felt or wine cork works very well).  Finally, with the sustain pedal fully depressed, loosen the upstop rail's screws and let the rail drop down to contact the damper levers at this point of maximum travel.  Retighten the screws.  The damper and trapwork system will now function with consistency and predictability, with the pitman-pin remaining securely in its proper position at all times.