This is a CY 34mm piston / ring that has been CNC lightened and modified by CAT 5 Manufacturing.  Fits Chung Yang CY26RC (aka "Fuelie") 26cc engines that are commonly found in HPI Baja 5B / 5T.  This piston is 23% lighter than stock allowing the engine to spool-up faster, rev higher, and give better overall performance.  The inside of the piston has been stripped of it's excess material making the piston lighter and better balanced.  The top of the piston has been modified to resist "lean siezures".  A lean siezure is a condition that happens when an engine's fuel mixture is too lean, causing excessive heat build-up to the piston and cylinder.  As the engine gets hot, the top of the piston will expand to the point where it will start dragging the cyliner walls causing the aluminum of the piston to smear across the piston ring siezing the ring into the piston.  This will cause the engine to lose its compression and make the engine not run.  CAT 5 has "turned-down" the outer diameter of the piston on both sides of the ring groove to protect the piston ring from lean siezing.  This procedure does not reduce the engines compression, but instead, reduces the surface area of the piston skirts thus reducing parasitic drag between the piston and cylinder.  This lightened piston is a must for any racer or basher who is looking to get more performance out of his stock or modified engine. 

 

Also fits Zenoah G260RC / G270RC / G260PUH / G260PUM engines.