Generally, an engine is made up mainly of various metal alloys, so the material used in the engine and its components can be recycled. The most important structural materials in 4-stroke engines are cast iron, alloy and structural steels, and aluminium alloys. Moreover, it also depends on the manufacturer what all material they use.
For this, we would suggest you walk into the nearest authorized service centre as they will be the better people to assist you. You can click on the following link to see the details of the nearest service centre and selecting your city accordingly - Service centre.