The Ins and Outs of a Motorcycle Engine
How familiar are you with a motorcycle engine? Whether you’re a seasoned biker or a first-time rider, watch as motorcycle enthusiast Matthew Bochnak explains what makes up a motorcycle engine.
MATT: Hey what’s up everyone, it’s Matt from HowToMotorcycleRepair.com.
MATT: In this video, I want to show you what is actually inside a motorcycle engine.
MATT: I’m currently in the process of rebuilding a four-cylinder engine and have hundreds of parts laid out on my workbench.
MATT: So, let’s take a closer look and see what’s inside this engine.
MATT: There are three main sections that make up a motorcycle engine: the top end, the bottom end and the gearbox or transmission.
MATT: Let’s start with the top end, which consists of the valve train, cylinder head, cylinder and pistons.
MATT: Underneath the valve cover, you’ll find the valve train, which is responsible for opening and closing valves at certain times to allow the fuel and air to mix in and exhaust gases to exit.
MATT: A camshaft with eccentrics, which is this egg-shaped component, rotates and pushes the valves open.
MATT: On overhead valve engines, which are standard on most motorcycles and cars, there’s a rocker arm between the camshaft and valve and these parts operate like a teeter totter.
MATT: The bottom end consists of connecting rods and a crankshaft.
MATT: These parts are responsible for converting linear piston movement into rotational motion, like so, and they are sandwiched between the engine cases.
MATT: In order to access these components, the engine cases need to be disassembled.
MATT: This is also known as “splitting the cases.”
MATT: The crankshaft and connecting rods ride on bearing shells that have a slippery surface that allows these parts to rotate smoothly.
MATT: The last section I’ll show you is the gearbox, which is made up of the clutch and the transmission.
MATT: The rotational motion from the bottom end is transferred to the clutch.
MATT: The clutch is nothing more than a mechanism to allow power to be cut off from the engine to the transmission.
MATT: When the clutch is pulled in, the bike will act as if it is in neutral, the engine and gearbox are coupled and power will be transferred all the way to the rear wheel.
MATT: The transmission is also located in the gearbox and is made up of a bunch of gears.
MATT: Some of these gears slide in order to mesh with smaller or bigger neighboring gears, and can produce different gear ratio (or speeds), depending on the speed the rider desires.
MATT: Shift forks slide the gears one way or another.
MATT: The shift forks are moved by the shift drum.
MATT: The shift drum gets rotated by a gear shifter.
MATT: As you can see there’s a lot going on inside a motorcycle engine.
MATT: And once you take an engine apart and lay out all the components on a workbench, it’s fascinating how many parts there really are.
MATT: All these components are cleaned up and ready to be assembled, with new bearings, seals and gaskets.
MATT: Once the rebuild is complete, this engine can go back into service for years to come.
MATT: Well, I hope you enjoyed this video on what’s actually inside a motorcycle engine.
MATT: If you’d like to see more of my videos, head over to HowToMotorcycleRepair.com, or check out my YouTube channel, MatthewMCrepair.
MATT: I’m also on Facebook and Twitter.
MATT: Thanks for watching and see you next time.