2003 Polaris ATV Trail Boss 330 Factory Service Manual, Page 81Get this manual
ENGINE 4Apply clean engine oil to the piston rings, ring lands, piston pin bore, piston pin, and piston skirtLubricate the connecting rod (both ends) and crankshaft main bearing area5Install the piston on the connecting rod with the pin casting notch facing the rear of engine (starter side)The piston pin should be push fit in the piston2Apply clean engine oil liberally to the cylinder bore and tapered area of the sleeveInstall the cylinder with slight rocking motion until the rings are captive in the sleeve
6Install the other circlip with the gap facing up or down(See Caution with Step above)Push the piston pin in both directions to make sure the clips are properly seated in the groove7Place the dowel pins in the crankcase and install new cylinder base gasket8Lubricate the piston and rings with assembly lube and install sleevetype ring compressor on the piston assemblyVerify that the ring gaps are 120 degrees apart from each other before installation