Teardown: Basics of how a motorcycle works

A rite of passage for many gearheads is taking apart an internal-combustion appliance and learning how its metallic innards work. Many lawn mowers died in my parents’ driveway, never to run again. Tearing down those bumbling four-stroke single-cylinders taught me a lot and set the framework for the diagnostic process I still use today. Not everyone has the time, tools, or space to learn that way, though, so it was awesome to see FortNine post a video tearing down a simple two-stroke motorcycle and explaining the function of each part as it came off the bike.

This video covers only the basics, and it’s easy to critique FortNine for skipping this or that; but for a square-one enthusiast, this video captures a wonderful, high-level picture of where parts are and why they exist. This basic framework can be tough for beginning enthusiasts to grasp when working alongside someone more experienced who may snap through tasks with relative ease. Interrupting someone just to ask, “Wait, what is that part and why are you removing it?” can be intimidating. The internet saves the day—sort of.

The Suzuki TC90 featured here is a bare-bones, two-stroke machine that looks to have been produced a good 50 years ago. It contains everything needed for locomotion and nothing extraneous. For example, it does without camshafts. The two-stroke cycles of the engine allow it to draw in fresh air and fuel and exhaust those spent combustibles through ports in the cylinder. A four-stroke machine needs valves to allow those functions to occur. In most modern engines, those valves don’t act on their own and thus need a camshaft to orchestrate the opening and closing to ensure proper running.

The other item left out of FortNine’s tidy explainer is the meshed gears that compose the transmission. A manual gearbox is fairly easy to comprehend, since it simply multiples torque by exploiting differences in gear size. Most folks are at least somewhat familiar with the concept since 10-speeds became the norm for bicycles decades ago.

We all had to start with the essentials. There is nothing wrong with how the world has shifted the starting point for mechanical knowledge from a wrench in hand to a mouse and keyboard beneath your fingers. With a little more knowledge going into their first projects, enthusiasts these days might have a better chance of seeing their vehicle start and run.

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