Spark plug NGK CR7HSA - ZNEN ZN50QT-E. Original suppressed spark plug for 99% of all 50cc China 4-stroke scooters equipped with a tachometer. Tachometer only work properly using suppressed candles. NGK spark plugs are used worldwide in all vehicle categories. From the original engine to racing, NGK is one of the top manufacturers of spark plugs. And it is important to install a high-quality spark plug, as the cost of engine damage is in no relation to the price of a good spark plug. The right heat value is the most important thing when choosing the spark plug. Too hot candle may result in engine damage and one too cold can lead to constant soot. Therefore, it is important to always use the same heat value as that of the original candle for unthreaded mortenings. For sports and racing engines, it is advisable to use a slightly colder candle.