DW FAN WRITES IN: “At one of our riding stops at a recent club ride, the topic came up that if you increase the spark plug gap it will increase horsepower. If that is so, then why don’t the manufacturers do that from the factory if it is that simple?” – Jackson Easton, Las Vegas, NV.

OUR PRO ANSWER: Simple question with a not so simple answer! Increasing the gap on a spark plug electrode can increase horsepower but only if the ignition system is woefully underpowered and the engine can barely run with the stock ignition (Think Yamaha RD250 / 350).  And you install a more powerful ignition. Then and only then does the horsepower of the engine increase by opening up the too-narrow spark plug gap utilized because of the underpowered ignition system. The wider gap allows more of the fuel / air mixture to get between the spark plug’s center electrode and the ground electrode. A side benefit of a larger gap with the accompanying high-output ignition is the spark, once generated, will last longer (spark duration) because of more ignition coil energy available. This makes the engine more “crisp” and responsive to throttle. Technically, as soon as the spark is created, the gas around the spark plug’s electrode is ionized, and this drastically reduces the electrical requirements to maintain the spark. The more energy available after the initial burst of energy generally allows for a more complete burn in the combustion chamber. So, does that mean more horsepower? Only if the ignition system can handle the increased initial voltage requirement because of the wider spark plug gap. If not, there may not be enough ignition power to jump the wider gap of the spark plug, thus creating a misfire. My advice, Son, is to stick with the stock spark plug gap unless you have installed a higher output ignition system. Today generally the manufacturers have done enough testing to figure out what the correct spark plug gap should be for most driving conditions. The most that may need to be tinkered with is the spark plug heat range. But that’s another column in itself.

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