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Tue May 04, 2021 11:59 am

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?



Tue May 04, 2021 1:02 pm

If there's any risk running the hotter plugs I'll pull them out. Having just bunged them in, I now know it's not such a hard job.

Checking the net for plug prices, I found Spark Plugs Direct in Sunbury Vic. They're charging $10.05 per plug and free shipping for orders over $49. Five plugs gives me a spare and free shipping!

https://www.sparkplugsdirect.com.au/pro ... 0926&_ss=r



Tue May 04, 2021 4:32 pm

It's called playing with fire. Pun Intended. As the results would very much be the same.
You have selected a plug with a hotter heat range than that recommended. The effect of this in the long run would be burnt out valves and erratic working of the engine. Continual use could cause permanent damage to the engine.
If you like your bike, get the original spec spark plug.

I use iridium plugs, with the correct heat range. Excellent starting.


Wed May 05, 2021 5:12 pm

Thanks Bill,

Looks like the iridium equivalent of CR9EKs might be CR9EIX.

I bunged a turbo on a Datsun 40 years ago and had to run colder plugs. With the extra cylinder pressures, I had to replace them twice as often. Up until the point where I fitted electronic ignition and then they'd last longer. The problem was that the cooler plugs would soot up with quiet driving and didn't come good until they copped a bit of heat.



Thu May 06, 2021 9:52 am

"Looks like the iridium equivalent of CR9EKs might be CR9EIX."

.....would sir like finance with the 4 spark plugs.....expect north of $20 each (australia tax at work)

:shock: :lol: :shock: :lol: :shock: :lol: :shock: :lol: :shock: :lol: :twisted:


Thu May 06, 2021 2:16 pm

One number difference on it's own wont have any affect. They all have a range and plug(heh!) for somewhere in the middle of the compromise curve.

Other factors are if you:

> have any modifications that improve power output
> have advanced the spark from stock
> are having any issues with your cooling system
> live in the northern extremes of Oz {ie you put a jumper on when it drops below 30deg}
> use regular unleaded petrol
> ride it like you stole it - as in ALL THE TIME
> stole it

If you can tick two of these, then you might start to get to marginal conditions. The plugs will show signs of running too hot long before detonation sets in, but when it does, umm... better go steal another one!



Wed May 12, 2021 11:38 am

Make sure you buy the plugs from reputable store too, not ebay.

I bought 4 iridium plugs and from visual inspection I knew they were fakes. Threw them away.


Thu Sep 23, 2021 1:18 pm

If your exhaust is quite dark (rich) then they won't hurt, maybe even help, but if your exhaust is running as grey as a ghost then you need to address the tune and do not run hotter plugs.
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