genuine-parts-spark-plugs-comparisonComparison between LMAR9E-J and CR9EIA9
For spark plugs, it is important to locate the spark in exactly the pre-determined area of the combustion chamber, to assure optimal engine performance. Engine design factors, such as the shape and size of the combustion chamber, the number and size of intake and exhaust valves and angle of the valves are all aspects to be considered when choosing a spark plug. If is not possible to find the correct spark plug during the engine development stage, Yamaha engineers will design and develop a totally new one.

For example, the 2009 and later model YZF-R1 has a high rpm, large bore and short stroke engine, offering increased engine power and wider heat range. Previous spark plugs designs could not be fully cooled, so long reach plugs, with a very long thread body were developed.

It is therefore important to use the specified spark plug, forany model, for both maximum engine performance and to avoid damage to the engine.

Spark Plug lifespan for optimal performance in the long run
Even in normal use, spark plugs require periodic replacement, since those that have been used for a long time, will have started to degrade, possibly misfire more often, causing preignition and consequently result in lower engine performance and reduced fuel economy. Eventually it can even lead to severe damage to the engine! With all this in mind, Yamaha have selected the best possible spark plugs for every model in their range.