1888a123_Beginner_Dirt_Bike___GICL_Wiki_Dirt_Bike_Parts_List_Function
[Part and Quantity] Chain (1) [Part Number] DR70-046 [Materials] Metal, most likely steel for its strength and resistance to wear because of friction [Forces] There would be a friction force between the chain and the gears. There would also be a tension force between the chain links. [Manufacturing Process] Individual chain links pinned together with the correct spacing needed for the gears used to create a flexible belt. [Shape] Shape and size is determined by several factors. One is the spacing between the engine and the wheel. The spacing of the links is determined by the gears that are being used. [Part Complexity] 4 [Function] 
Functional: used to connect the engine to the rear wheel, and transfer energy between the two.
Group 11 - Beginner Dirt Bike - GICL Wiki