What does a cylinder head do and why is it a vital part of a motorbike engine? The main job of the cylinder head is to hold the parts that allow the fuel/air mix into the engine and the exhaust gases out of the engine.
The cylinder head in a Kawasaki ER5 engine
The cylinder head sit’s between the cylinder head cover and the cylinder barrel.
The head sits under the cylinder head cover (top pic) and on top of the cylinder barrel (bottom pic)
The main parts the cylinder head contains are:
- Outlet (exhaust) cam shaft
This controls when the exhaust valves open and close.
- Inlet (fuel/air) cam shaft
This controls when the fuel/air valves open and close.
- Exhaust valves
These let the exhaust gases out of the cylinder barrel after the spark has burnt the fuel.
- Fuel/air inlet valves
These let the fuel/air mix into the cylinder barrel.
- Cam chain (this does run down the engine to the crankshaft)
This chain runs from the crankshaft up to the cam shafts and rotates the cam shafts so they can open/close the valves.
- Cylinder head bolts
These bolts run the length of the engine and clamp the crankcase, cylinder barrel and cylinder head together.
- Spark plugs
These ignite the fuel/air mix in the cylinder barrel.
Cylinder head with the cover removed showing the different parts.
The cylinder head mainly lets the fuel into and exhaust gases out of the cylinder barrel. The cylinder head also holds the spark plugs so, when attached to the bike engine the sparking end of the plug sits on the top of the cylinder barrel.
There are also a few odd holes around the cylinder head to allow engine oil to lubricate the moving parts.
Basically, the valves let fuel/air mix into and exhaust gases out of the cylinder barrel, the cam shafts control when the valves open and close and the spark plug ignites the fuel/air mix in the cylinder barrel.
Cylinder head with the camshafts removed showing the valves and cam seats.
Cylinder head bottom (the part that sit’s on the barrel) showing the valve bases and spark plug heads.
There are alot of fast moving metal parts in the cylinder head that come into contact with each other and operate at high temperatures which is why it’s IMPORTANT to use a good quality motorcycle oil and change it at the recommended intervals!
Close up of the top of the cylinder head with the cam shafts removed showing the valves, cylinder bolts and spark plug tops.
Close up of the bottom of the cylinder head showing the plug heads and the valve bases
Note – The bottom of the cylinder head (where it’s sits on top of the barrel) is discoloured due to the fuel burning in the cylinder barrel.
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