Description
Note: only goes with Polini Evolution 70cc cylinders (series 1, 2 and 3).
Cylinder head
The cylinder head of an internal combustion engine can have different shapes and contain different elements, depending on the type of engine. While in a two-stroke engine the cylinder head contains only the spark plug, in a four-stroke engine it is much more complex, as it also contains the valves, the camshaft and many other parts that are important for the operation of a 4-stroke engine.
However, these two points apply to any cylinder head:
- it must be tight
- it controls compression
Different types of cylinder heads
Each cylinder head is specifically designed for a specific cylinder. You must therefore always make sure that the cylinder head fits the cylinder.
Cooling :
The cylinder head is also partially responsible for cooling the engine. In air-cooled engines it has fins on the outside and in liquid-cooled engines there is chamber for the circulating coolant.
One-piece or two-piece 2-stroke cylinder head
One-piece cylinder heads are the most common, but modular two-piece cylinder heads are also available for 2-stroke engines. The principle is quite simple: the water jacket allows water circulation, while the combustion chamber insert closes off the combustion chamber. The cylinder head can be replaced and modified to achieve different compression ratios and thus different engine behavior.
4-stroke cylinder head
Tuning cylinder heads can also be found for four-stroke engines. Although components optimized for motocross are seldom found on the market (usually they are original components that have been reconditioned to increase performance), there are also racing cylinder heads for scooters and motorcycles. These often have optimized intake and exhaust ports and sometimes even seats for larger valves.