How often do you change a spark plug, since I bought the Honda CB400 one year back I did not changed the spark plugs.

How often do you guys change the plugs on your bikes? Is it done for performance reasons or just to be on the safe side?

We change our spark plugs once every six months (whether we think the motorcycle needs it or not). Additionally, if we notice any deterioration in performance, sputtering or backfiring, we change the spark plug immediately.

Four strokes do not “oil foul” plugs like two-strokes. Instead, they suffer from gap erosion. What is gap erosion? As the spark jumps the gap from the sharpest edge of the plug's electrode, it eats away at the electrode and the ground strap. When the sharp edge is worn down, it becomes harder for the spark to jump the gap.

You should never run a spark plug long enough for gap erosion to become a performance problem.

The best advice is to use Iridium IX spark plugs, they offer extreme ignitability, improved throttle response and superior anti fouling. The fine Iridium tip ensures high durability and a consistently stable spark.

Iridium alloy has extremely high melting point, perfect for today’s high-tech, high-performance engines. The Trivalent Metal Plating used had superior anti-corrosion and anti-seizing properties.

Using the Iridium IX spark plugs give you outstanding acceleration, high fuel efficiency and durability...

The Honda Phantom reccomends inspection at 4000 and change every 8000. Here they don't service properly so the plugs stay in until they breakdown. As mentioned you can get missing and backfiring when the insulation breaks down owing to overheating.

On modern motorcycles standard spark plugs and coils these days are extremely good, and service schedules often leave spark plugs for 20,000 kilometers between checks. But spark plugs don't last forever, and small deficiencies can cause slight misfires at high rpm that cut power.

Pull your spark-plugs out and check for cracks in the ceramic insulation or oil/water in the spark-plug tunnel.

If the motorcycle's fueling isn't perfectly set-up this can wear down the life of a spark plug as well. Some fine grit sandpaper can help freshen an old plug, but ideally you'll replace the spark-plugs with the recommended good quality spark plugs, not cheap no-name Chinese from the automotive shop around the corner.