Re: Bad or Good - Look at this Piston
that my friend is called detonation.<br /> the fuel to air ratio leaned out and the hottest part of the piston is the ring land near the exhaust port. I dont see any evidence of piston siezure just detonation. usually caused by a clogged carb or a weak fuel pump and continued high speed running even after you noticed it was sick. when a motor like a high performance 2 stroke tells you its sick it dies soon without treatment.<br /> it looks like a nice freshwater motor that will be worth a rebuild. make sure you find and correct the cause of the detonation.<br /> overadvaced timing usually detonates the intake side of the piston.<br /> either way have a machine shop carefully measure the pistons and the bores for correct diameters that still conform to specifications. if its honed the measureing and math has do be done after honeing. the piston ring looks mostly intact so its doubtful it was a piston ring locating pin failure. more like a maint issue that got run till it was a mechanical issue.<br /> in any event a thorough tune up of the cooling and fuel system will need to be done at reassembly. but the only way to know if there is any other damage is to disssemble it.<br /> if you wish to reuse any bearing assy´s make sure you keep them in pairs at disassembly and always use the correct sealants and new rodbolts on reassembly. I am with Ray on the piston wristpins. I would replace them,using new circlips, anytime an older engine is apart.<br /> if you dont replace them at least remove them and very very carefully measure them, the tolerance is very very tight.something like .0003" to .0006" from a nominal size.<br /> but mechanically no its not a wear issue that caused the failure,in my opinion from the pictures, it was a routine,or lack of, maint issue that caused the failure. usually if the wall wears enough to form a ridge the rod bearings will get loose and fly apart, or that thin wristpin will, long before the piston fails.
