Electricity Basics

by fldptr

px 200 electricity

Unmounted dashboard of a PX200 Vespa.

How much of motorcycle science is mechanics? That’s what most people think of when it comes to repair or tuning. Well, it’s a lot more diverse then just that. There’s a spectrum of natural and engineering sciences involved, including fluid mechanics, material sciences, thermodynamics (just think about what’s happening in the cylinder!), a lot of chemistry (fuels, lubricants, batteries), and yes, there is Electricity. With a capital E.

Could a bike work without it?

Maybe. Allow me another question: What’s the difference between Diesel and Otto (petrol) engines? The most significant is the spark plugs, which are essential to ignite the gas-air mixture in the cylinder, otherwise nothing would happen so to speak. Diesel engines don’t have spark plugs, but the movement of the piston compresses the mixture to the ratio where it self-ignites. It’s a working cycle, without electricity.

The truth is that not a lot of diesel bikes had been built throughout history, and even those probably had electric supply and system for electric start, lights, dashboard or signals which are essential for any motorbike. Today’s motorbikes however have even a lot more taken care of by electricity, some of which make them more reliable, faster, during, and some just help the engineers to solve design problems.

In the early 90’s, the place of carburateurs started to be taken by fuel injection systems, in cars and motorcycles as well. This system has a lots of advantages to carburateurs, but to achieve those, it needs to rely on information from sensors hidden at many parts of the bike. It’s not coincidential that the revolution of fuel injection happend when the personal computer and intergrated circuit industry boomed. Modern bikes have their electric brains, actual computers, usually called ECU or PCM. These words refer to expressions such as ‘Engine Controlling Unit’, therefore when you ask:

Does a Mechanic need to know all about this?

You’ve got your answer. It’s a deep science and perhaps it’s almost impossible to know and learn all about integrated circuits and the material sciences of pistons at the same time. It’s just not the same genre at all. But even if you’re a fan of kickstarter bikes with no lights and battery but just a spark plug cable, knowing how electric systems on modern bikes work could even help you to amend your old bike, in many more way then you might think.