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2 Stroke Engines – Operating Principles


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Component Parts
2 Stroke Engines – Operating Principles
John H. Glimmerveen Licensed to About.com

So how does a 2 stroke work? First it is necessary to become familiar with the major component parts:

  • Cylinder head (A)
  • Cylinder (B)
  • Ports (D = inlet, H = exhaust)
  • Piston (C)
  • Connecting rod (E)
  • Crankshaft (F)
  • Crank cases (G)

Starting at the top, the cylinder head is dome shaped to create a space for the combustion of gases (gasoline and air mixed). Screwed into the cylinder head is a spark plug. Most 2 strokes utilize a single, centrally located plug. However, many different designs have been tried, including twin plug heads.

The cylinder head is bolted to the cylinder (typically with 4 bolts). The cylinder contains various ports: inlet, exhaust and transfer (more about those later).

Supporting the cylinder and cylinder head are the crank cases-so called as they also carry the crankshaft. 2 stroke crankcases are split vertically on most designs; however the Japanese manufacturers preferred horizontal splitting cases on all of their engines with more than one cylinder. This horizontal splitting of the cases made assembly and disassembly much easier.

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