How Do You Understand Compression And Power Systems In Small Engines?
• Understand the basic function of the engine. The engine is an air pump. The more air, the more power. • Become familiar with how compression works. The engine has a stroke, which is the travel of the piston up and down the cylinder. The amount of room in that cylinder is described in terms of cubic inches (or centimeters) with the piston at the bottom of the cylinder. For example, a 351 Ford has 350 cubic inches. The compression ratio is a comparison of the volume (with the piston at the bottom) and the space left with the piston at the top of its stroke. Most lawnmowers are low compression engines, with ratios of 8:1 or less. This is why they run well on cheap gas (87 octane). Diagnosing problems: If you have a compression problem, the engine won’t run (in 99% of cases). The best indicator of low compression is the engine pulling through too easily. If you hit the starter and the engine spins like crazy (unusually fast), you will need to check the compression with a tester. This is
