CPS TRS-21 Piston Inspection and Maintenance

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.

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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.

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    3 Discussions

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    The real Big Papi

    8 months ago on Step 7

    You left out a criticle step by not including the removal of the top piston ring and the o-ring that is hidden beneath it! I use the same plastic pry tools that are used for cell phone repair to remove the ring. A metal tool should never be used because of the risk of damaging both the piston and rings