Lift truck Engines
Forklifts are classified as small-engine vehicles, the same class in which lawnmowers are categorized. The engines of the forklifts all follow the principles of internal combustion. Various lift truck brand names and models would have varying engine layout and design. Forklifts are designed more toward producing high torque than for speed. They normally are geared to low speeds. The engine powers the drive wheels of the forklift. The engine is also required to lower and lift the forks through a series of chain pulleys. Nearly all modern forklift engines are powered by propane as they would be used indoors, where diesel and gasoline engines would be unsuitable because of the exhaust they make.

Normally, the lift truck is a four-cylinder engine-block. Forklift engines are similar to car engines as they contain pistons connecting to a camshaft. Each and every cylinder head has an exhaust hatch, a spark plug and an exhaust hatch, each of them one-way and spring-loaded.

Engine Function
When the driver starts up the engine of the forklift, propane passes through the opened throttle-plate in a fine spray and mixes together with air which comes from the mass air intake before moving into the cylinder head intake hatches. Every one of the four pistons is staggered to rise in a precise sequence, compressing the propane and air mixture as every piston rises to the top of the head. With timing which is really precise, the engine's alternator and battery create an electrical current that passes through the spark plug. The fuel ignites causing an explosion which drives the piston back down to the bottom of the cylinder, resulting in a continuous turning of the camshaft. In the cylinder, an air pressure imbalance causes the the exhaust hatch to draw out exhaust when more fuel passes into the cylinder. Propane burns cleaner compared to gasoline and diesel and the exhaust is not as harmful.