Surging is more to do with fuelling than ignition. There's not a lot to be gained from changing to a different spark plug from that recommended by Yamaha. You could get an iridium plug (CR7EIX), but to be honest they won't make any difference to performance, they are simply designed to last longer.

The main thing is to make sure you have a decent quality, correctly gapped plug that is in good condition. Watch out for fake NGKs which proliferate ebay; these can detrimentally affect performance and have been known to shed insulators with serious consequences.

Spotting fake plugs - http://www.ngk-sparkplugs.jp/english/techinfo/fake/

BTW - I've moved this thread to the appropriate section for you.

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