2005-2008 Honda ATV TRX500FA/FGA Fourtrax, Rubicon Factory Service Manual, Page 147Get this manual
COOLING SYSTEM Remove the two bolts and thermostat coverBOLTS THERMOSTAT COVER
Remove the thermostat from the cylinder headRemove the seal rubber from the thermostat
SEAL RUBBER
THERMOSTAT
INSPECTION
Visually inspect the thermostat for damageMake sure the rubber seal on the thermostat is in good conditionReplace the thermostat if the valve stays open at room temperature or the rubber seal is damagedKeep flammable materials away from the electric heating elementDo not let the thermometer or thermostat touch the pan, or you will get false readings