What is the spark plug model for a 125cc motorcycle?
4 Answers
125 motorcycle spark plug model is 2198. The spark plug is a crucial component in the ignition system of a gasoline engine. It introduces high voltage electricity into the combustion chamber and causes it to jump across the electrode gap to generate a spark, thereby igniting the combustible mixture in the cylinder. The spark plug mainly consists of a terminal nut, insulator, terminal stud, center electrode, side electrode, and shell, with the side electrode welded to the shell. A 125cc motorcycle specifically refers to motorcycles with an engine displacement of around 125cc. Major motorcycle manufacturers have launched various brands of motorcycles with engines based on this displacement. In China, brands with 125cc engine motorcycles include Suzuki Haojue, Prince Motorcycle, Honda, BMW, Yamaha, and others.
I've been working on motorcycle repairs for over 20 years, and there are only a few common spark plugs for 125cc engines. The NGK C7HSA is the most common one, used on old CG125 and Haojue models. Yamaha models prefer the D8EA, which has a slightly higher heat range. Domestic models like 1136 and 1137 are also common, and some Wuyang-Honda bikes come with these. The key is not to just look at the model numbers—the standard thread length is 18mm, and a heat range between 6-8 is the safest. Last time, a young guy replaced his with the wrong heat range, and his bike started misfiring—turned out the spark plug was overheating and causing pre-ignition. If you want to be sure, just check the stamping on the old plug—it’s the most accurate way, and you can also check for carbon buildup while you're at it.
I've been commuting on a 125cc bike for five years and changed spark plugs three times. I've roughly memorized the common models: NGK's C7HSA suits most domestic bikes, which is what I use on my Qianjiang cruiser; D8EA is commonly found in joint-venture bikes, like my friend's Honda Weiwu. There's also Bosch's WR7DC, which comes with some European bikes. The key is not to cheap out on no-name brands - last year I got lazy and replaced mine with an unknown brand at a small shop, only to have cold start issues later when I found the electrode gap wasn't even compliant. It's best to check the factory manual before changing, or post photos of your spark plugs on motorcycle forums to ask veteran riders. By the way, the upgraded iridium DR8EIX is more expensive but definitely gives smoother acceleration.
During the last maintenance of my 125cc motorcycle, the mechanic mentioned some details about spark plugs. There are generally three common types: NGK's C7HSA has fine and long threads, mostly used in scooters; those starting with D, like D8EA, are suitable for cross bikes with more durable electrodes; and the domestic T1137, commonly stocked in repair shops. Remember, the higher the heat range number, the more heat-resistant it is. For long-distance riding, it's best to choose a 7 or 8. Last time, my spark plug was leaking electricity, causing the bike to jerk during acceleration, but replacing it solved the issue immediately. It's recommended to check the spark plug every 5,000 kilometers. If it appears white, it indicates a lean air-fuel mixture, while a blackened plug suggests a rich mixture.
