Spark plugs live a hard life: high pressure, extreme temperatures, and constant explosions. Should we be surprised that the OEs expect us to check the conditions of our bike's plugs at every service? If you look at your manual, that should be just about every 4,000 miles. Fortunately, the plugs don't often need replacing, just a quick brush off. Still, don't let spark plugs' hardiness lull you into a false sense of confidence. Few things can wreak havoc on your engine's performance like a fouled plug. Luckily, checking and replacing your plugs is an easy job, requiring little more than a deep socket of the appropriate size, a torque wrench, a brass brush, and a wire spark plug gauge.