I just fitted new NGK plugs to my 2006 ZRX1200. Just pulled out the factory plugs after 14 years and 34,000 kms.
The bike had become hard to start. Speaking to mechanics, some say that the plugs don't need to be changed at 34,000 kms. Others say that they need to be replaced at 24,000 kms. Whatever's the case, the new plugs have the bike starting heaps better and that's a big plus.
The plugs I fitted are one heat range HOTTER. I removed CR9EKs and fitted CR8EKs. I bought the hotter plugs when the bike was running a bit rough and only cleared itself with a big rev. By the time I'd figured out that the rough running was an Optimax issue, I already had the spare CR8EK plugs on the shelf. Am I likely to encounter problems running plugs one heat range HOTTER?
PAH