2012 Sportsman 400/500 and EFI Tractor Service Manual 9923412, Page 104Get this manual
ENGINE 5Install the top ring (chrome faced) with the "R" mark facing up and the end gap facing forward (toward the exhaust)Ring Profile 4Apply clean engine oil to the piston rings, ring lands, piston pin bore, piston pin, and piston skirtLubricate the connecting rod (both ends), balancer drive gear, and crankshaft main bearing area5Install the piston on the connecting rod with the arrow ormark facing the magneto (RH) end of the crankshaftThe piston pin should be push fit in the pistonMark-up Top
Second Mark-up 6Check to make sure the rings rotate freely in the groove when compressed6Install the other circlip with the gap facing up or down and tang outward(See Caution with Step above)Push the piston pin in both directions to make sure the clips are properly seated in the groove
Piston Installation
1Clean the gasket surfaces on the cylinder and crankcaseRemove all traces of old gasket material2Make sure the cylinder mounting bolt holes are clean and free of debris3Install new circlip on one side of the piston with the end gap facing up or down, and tang outwardTang Outward