It is a popping resonating sound generated by a lean condition on deceleration. When you suddenly close the throttle, the incoming air is choked off and the closed throttle also causes the bike to return to idle on the very lean idle circuit.
The reactivity series of metals was deduced by performing several experiments in the lab which enabled scientists to arrange metals according to their reactivity with dilute acid, oxygen (air), and water.xides of iron and copper are insoluble. Metals that are less reactive than copper like silver, gold and platinum do not react with oxygen. Note: When aluminum reacts with oxygen, a layer of aluminum oxide adheres and covers the aluminum.
A metal will displace (take the place of) a less reactive metal. in a metal salt solution. This is similar to the non-metal displacement reactions. seen on page 23 of the periodic table. For example, iron + copper(II) sulfate iron sulfate + copper. Fe(s) + CuSO4(aq) FeSO4(aq) + Cu(s) Copper(II) sulfate is blue, iron sulfate is colourless. During the reaction the blue solution loses its colour. and the iron metal is seen to turn pink-brown. as the displaced copper becomes deposited on it.