An LPG forklift stores fuel as a liquid under pressure in a tank. A vacuum-operated fuel valve in the filter unit lets liquid reach the vaporizer only while the engine is being started or is running. The vaporizer, heated by engine coolant, drops the pressure and changes the liquid to vapor. The carburetor meters that vapor against airflow, and a governor limits engine speed.
A forklift mast is a set of nested weldments that slide on load rollers and strip bearings, raised by lift cylinders and chains. The carriage carries the forks and rides in the inner weldment. The checks that matter are roller and bearing clearance, chain length and tension, and internal hydraulic leakage. Mast parts are heavy and can move, so the safety procedure must be followed.
A forklift steering axle carries the steered wheels. It hangs from the frame on a center pivot pin so it can rotate as the truck travels over rough ground, and a hydraulic cylinder with a rod out of both ends pushes tie rods to swing two spindles on their king pins. Each spindle and each hub turns on a pair of tapered roller bearings.
A tilt cylinder is a double-acting hydraulic cylinder that tilts the mast. Oil behind the piston pushes the rod out and tilts the mast forward; oil in front of the piston pulls the rod back and tilts it backward. The number and design of the parts differ between trucks, but the operation is the same, and most repairs come down to renewing seals.
Cushion tires are solid rubber on a base band, made for smooth indoor floors, tight aisles and low clearances. Pneumatic tires are larger and deeper-treaded, made for rough ground and outdoor yards. The choice is usually made for you: cushion and pneumatic trucks are different machines, so the surface decides the truck before it decides the tire.