2010 Polaris Sportsman 850 Service Manual, Page 132Get this manual
ENGINE Cylinder Head Assembly
NOTE: Assemble valves one at time to maintain proper order1234Apply engine oil to valve guides and seatsCoat valve stem with Premium Starter Grease (2871460)Install valve in guideValve seals should be installed after the valves are in the head to avoid valve seal damageInstall NEW valve seals on valve guides carefully with rotating motionDip valve spring and retainer in clean engine oilInstall spring with tight wind facing DOWN (toward head)3
Valve Sealing Test
12Clean and dry the combustion chamber area (A)Pour small amount of clean solvent into each intake port (B) and check for leakage around the valvesThe valve seats should hold fluid with no seepageRepeat for exhaust valves by pouring fluid into each exhaust port (C)