Honda PIONEER SXS1000 2016 Owner's Manual page 162

Coolant
3. Remove the front hood (page 125).
4. Remove the reserve tank cap.
Always add coolant to the reserve tank. Do not attempt to add
coolant by removing the radiator cap.
UNDER FRONT HOOD
LEFT FRONT
5. Add coolant to the reserve tank as required to bring the coolant
level to the MAX level mark.
6. After adding coolant, install the reserve tank cap and install the
front hood.
158
Servicing Your Honda
reserve tank cap