LOCATING PIN COMMON CAUSES OF FAILURE
Your Wossner two stroke piston was designed for high performance and reliability, using premium materials and manufacturing methods. It is the nature of a performance component to be under stress, and at times the stresses on the engine components can be severe enough to lead to failure. At times, the piston and components will become damaged due to many of these influences. This guide is to help understand what can cause failure so that this can be prevented in the future. The ring locating pins primary job is to prevent the piston ring from rotating. This is accomplished by either a back- notch ring or top-notch ring:
TOP NOTCH AND TOP LOCATING PIN
BACK NOTCH AND CENTERED LOCATING PIN
Your Wossner piston kit was designed as a system, using the proper piston ring and notch combination that will engage together. Always inspect that the piston ring has engaged the ring locating notch correctly during installation.
NOTE: If the piston ring has not engaged the locating pin during assembly, severe damage is possible to the piston, ring, and cylinder. Always refer to your OEM service manual for detailed instructions or consult a qualified engine builder. !
Once assembled properly, the piston, ring, and locating pin will operate correctly in the engine. Potential causes of locating pin failure can be: • Cylinder porting / chamfering not correct for smooth operation of the piston and ring (PIC 1) • Excessive heat causing the piston material to become annealed, and loosening of the locating pin followed by failure. This phenomenon can be verified by measuring hardness of the piston. • Erosion of the piston crown near the locating pin, as caused by pre-ignition or detonation from improper fuel or tuning (PIC 2) • Foreign material in the engine resulting in damage to the piston, ring, or cylinder
PIC 1: PROPER PORT CHAMFERING ALLOWS SMOOTH TRANSITION OF THE RING DURING TRAVEL
PIC 2: EROSION OF THE PISTON FROM DETONATION WILL ANNEAL THE PISTON MATERIAL, CAUSING FAILURE
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