My JH600 thanked me immediately with smoother idle and better performance when I swapped out the stock plug for an NGK Iridium, which cost about 70 rmb or US$11 as I recall. The stock plug was really crap -- discolored by gases that it clearly was allowing to pass from inside the cylinder. I probably could have gotten along fine with a standard NGK plug, but the Iridium works well and gives me peace of mind. I'm still thinking of getting a matching Iridium cable.

Without quality spark, nothing else on the bike matters!

NB: My brother's company sells cables for high-end audio equipment. US$8500 for a set of speaker cables! For a bit of fun, read through a few of the comments about this particularly product on Amazon....