2006-2012 Honda TRX90 TRX90EX/X Service Manual, Page 112Get this manual
CYLINDER HEADVALVES ASSEMBLY CYLINDER HEAD EXHAUST VALVE
CAMSHAFT
Clean the cylinder head assembly with solvent and blow through all oil passages ith compressed airInstall the valve spring seatsInstall new stem sealsLubricate the valve stems with eng ine oil and insert the valve into the valve guideTo avoid damage to the stem sealturn the valve slowly when inserting