Importance of Carbon Removal The removable of carbon is very essential to the life of the motor. It is the cause of much trouble and wear and tear, among other things a very troublesome and annoying knock. Its actions may be thus described: Under the heat of the explosion the carbon becomes incandescent and ignites each fresh charge of gas just as a spark plug does. But as it does this while the piston is coming up on the compression stroke, quite some time before the ignition should occur, the tendency of the resulting explosion is to drive the piston backward and cause a hard, metallic pounding to be heard. This, also, is what happens when the spark is advanced too far. It is a condition that should he rectified as soon as possible, as it is destructive to the motor in general and to the bearing in particular.