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.
Only a metal higher in the reactivity series will displace another. A metal can displace metal ions listed below it in the activity series, but not above. For example, zinc is more active than copper and is able to displace copper ions from solution.hose metals that can displace H + ions from acids are easily recognized by their position above H in the activity series. The boundary between the metals that react with water and those that don't is harder to spot.