Keep the mast chains and carriage bearings lubed. Periodically raise it to full height to "exercise" the mast components and keep it all working smoothly. Don't leave it stored outside for extended periods unless covered. The sun and rain will dry up the lube and UV rays will damage the rubber hydraulic lines. If you are ever lowering the forks and the chains go slack, the fork carriage could be hanging up due to worn carriage bearings or lack of lube. If that happens, they can suddenly fall and cause injury. Never stand under, or allow another person to stand under the raised forks, with or without a load.
