This guide will detail inspection and maintenance of pistons on the CPS TRS-21/TR-21. I am not a licensed repair technician so follow instructions at your own risk.
Step 1: Remove Fan Housing
Remove fan housing screws. one on top, one on each side.
Step 2: Remove Housing
remove screws from side of wiring housing, 2 on each side. pry the housing apart slightly at the rear and slide it out and off over the rear of the unit.
Step 3: Disconnect Pressure Sensor
separate spade connectors from Pressure sensor by pulling toward rear of unit
Step 4: Remove Handle Assembly
Using a 3/16 hex bit, remove the 3 screws securing handle to body of unit
Step 5: Remove Crankcase Cover
using same hex bit remove the 4 black nuts securing the crankcase cover, exposing the Pistons and cylinders and O-rings. Clean any grease off underside of cover.
Step 6: Remove, Inspect/clean Cylinders
pull up on cylinder while twisting back and forth until both come free. inspect for scoring and deposits on walls and clean with isopropyl alcohol as needed. Be careful not to lose O-rings on top of cylinder.
Step 7: Clean Piston Heads
gently pry the ring apart and slide over top of piston head. Clean rings and piston heads.
Step 8: Replace Rings.
Bend the rings inward slightly so they fit snug to the piston head, then pry slightly and slide over top of piston head into its slot
Step 9: Clean O Rings and Seat Cylinders.
Clean O-rings with isopropyl alcohol and lubricate with food grade silicone spray to enhance the seal, slide cylinders back over pistons and seat firmly.
Step 10: Replace Cover
replace cover with 4 black nuts. tighten securely so they don't loosen during operation, reconnect pressure sensor.
Step 11: Replace Housing and Fan Cover
secure housing to body making sure front of cover is flush, verify power switch spade connectors are still connected to power switc, then replace fan housing and screws.
Step 12: Attach Handle
reattach handle securely with 3 nuts.
Step 13: Test Pressure Shut Off Function
using provided caps, cover the outlet port tightly and start unit. Unit shut auto shut off within a few seconds. If it doesnt, verify the pressure sensor is connected.