NGK spark plugs have been around for a long time, they are an original fitment brand you can trust. These not a lot to say about plugs unless you want boring copy and paste technical details, a new one will work that's the main thing. If you are having engine issues always start with the easier (and usually cheapest) fix it solution which will be a new plug. The Spark plug R0409B8 has the 10mm thread and 14mm hex drive, you will need a special thin walled socket to remove it. For CRF 450R/X
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