Spark plugs provide the discharge needed to fire each cylinder in your bike’s engine. But over time they can be subject to all sorts of nasty wear and tear. The result is a bike that won’t go, or at least one that delivers on the expression “not firing on all cylinders”—an unsafe and potentially engine-damaging issue.
The eyes may be the windows to the soul, but sparkplugs are the windows to your engine. Removing a spark plug and inspecting it can tell you plenty about what’s going on in your engine. Is it running rich? Lean? Burning oil? Pull a plug and find out.
FOULING The end of the spark plug can be covered—or the gap between electrodes can be bridged—by dry or wet carbon (from fuel or oil leakage), ash (from excessive combustion deposits), or yellowish stains (from leaded fuels).
GLAZING When a spark plug overheats, deposits on the insulator or electrodes may melt and cover the surfaces, giving them a ‘glazed’ look.
MELTING Excessive heat or premature ignition can also burn the ceramic insulator or lead to the electrodes’ surfaces melting and becoming pitted and uneven.
EROSION The spark plug’s electrodes may become oxidized, corroded, or react with leaded fuel, and grow pitted, leading to a wider gap— thus drawing more voltage for ignition.
BREAKAGE The end of the plug may suffer damage from being struck by the piston (if the plug is too long), foreign objects in the chamber, or thermal shock from sudden heating or cooling.
DETONATION The insulator may be damaged if the electrodes’ gap is improperly set or if the fuel is causing engine knocking.
TIME Gradually, the ignition cycle does wear at the electrodes, widening the ignition gap and burning out the ceramic insulator.
Spark plugs provide the discharge needed to fire each cylinder in your bike’s engine. But over time they can be subject to all sorts of nasty wear and tear. The result is a bike that won’t go, or at least one that delivers on the expression “not firing on all cylinders”—an unsafe and potentially engine-damaging issue.
The eyes may be the windows to the soul, but sparkplugs are the windows to your engine. Removing a spark plug and inspecting it can tell you plenty about what’s going on in your engine. Is it running rich? Lean? Burning oil? Pull a plug and find out.
FOULING The end of the spark plug can be covered—or the gap between electrodes can be bridged—by dry or wet carbon (from fuel or oil leakage), ash (from excessive combustion deposits), or yellowish stains (from leaded fuels).
GLAZING When a spark plug overheats, deposits on the insulator or electrodes may melt and cover the surfaces, giving them a ‘glazed’ look.
MELTING Excessive heat or premature ignition can also burn the ceramic insulator or lead to the electrodes’ surfaces melting and becoming pitted and uneven.
EROSION The spark plug’s electrodes may become oxidized, corroded, or react with leaded fuel, and grow pitted, leading to a wider gap— thus drawing more voltage for ignition.
BREAKAGE The end of the plug may suffer damage from being struck by the piston (if the plug is too long), foreign objects in the chamber, or thermal shock from sudden heating or cooling.
DETONATION The insulator may be damaged if the electrodes’ gap is improperly set or if the fuel is causing engine knocking.
TIME Gradually, the ignition cycle does wear at the electrodes, widening the ignition gap and burning out the ceramic insulator.