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Discussion Starter · #1 ·
*As a disclaimer I did use that all-elusive search button and only found a couple threads on how to change plugs - pretty straight forward.

My question is, what is everybody changing them at? Mileage-wise.

I'm at 10,100 miles and the book says 8k intervals. I haven't noticed any power loss just a buggy twitchy throttle if I hold it steady in low gears (G2 tube installed).
I will be installing a new air filter this weekend and figure I'll do the plugs while I'm in there. Oem plugs will most likely be going in, but any suggestions on plug choice or recommendations are always helpful.

Engine wise bike is stock with Mobil 1 full syn every 4k miles.
Have run on the track twice this year but mainly commuting every day. :eagerness:
 

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"buggy twitchy throttle if I hold it steady in low gears"

Do you mean it has been getting worse with the miles?
 

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Discussion Starter · #3 ·
Unfortunately it seems that way. It's fine going through the gears. Holding it in say, 2nd gear around 30 you'll feel the bike lurch and kinda "chug" a bit, all while the throttle is held completely steady.
 

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I felt the same thing too. I did try some Denso Iridium plug that were suppose to be direct replacement but it didn't feel right so I got some OEM plugs... run better now IMO. The OEM are not Iridium, or at least Iridium is not stamp on it.
 

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I felt the same thing too. I did try some Denso Iridium plug that were suppose to be direct replacement but it didn't feel right so I got some OEM plugs... run better now IMO. The OEM are not Iridium, or at least Iridium is not stamp on it.
stock plugs are standard type, with a projected insulator. the problem with denso iridiums is, they don't have the built-in noise suppression resistor that the stock ones do. they work fine on some bikes, but could possibly cause weird issues with the f.i. and ride by wire. that might have been what you were feeling.
 

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stock plugs are standard type, with a projected insulator. the problem with denso iridiums is, they don't have the built-in noise suppression resistor that the stock ones do. they work fine on some bikes, but could possibly cause weird issues with the f.i. and ride by wire. that might have been what you were feeling.
Was worst at low load like cruising. Sort of engine cutting of for few .1 sec once in a while.
 

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I've been running the iridium NGKs for 7-8000 miles. It runs great and I gained a little bit of fuel mileage. You have to gap them larger than regular plugs or they can actually hurt performance.
 

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Discussion Starter · #12 ·
Thanks for all the feedback! I wonder why the service interval would be different across the pond?

If only it was like autos where the more "exotic" the metal, the longer they last essentially, but that'd be too easy. I'll be doin the swap this weekend. And since the engine is stock (for now) I'll stick with OEM. - In Yamaha I trust
 

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Maybe the UK and US counterparts call for different sparkplugs.. If not that I would blame it on US's emissions standards, marketing schemes, and legalities..
The theory behind the precious metal tipped plugs, is that precious metals take much much longer to oxidize, so they last longer...
... Throw a platinum nugget, copper nugget, and iridium nugget into the sea and see wich will tarnish first. Copper= fast, Plat= slow, iridium= super slow.
 

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I reckon if you pull the plug out and there is no obvious erosion of the tip, put them back in.
Put a small amount of chain spray on the threads and tighten the gasket down flat, then it won't loosen up or lose electrical grounding.
The chain spray means you can get the plugs out next time as well.
 

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I've never used any kind of spray on my plug threads... then again, I usually inspect them twice a year. YMMV :)
 

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While the US service schedule stats 8k the UK schedule states 12k miles.
I thought you guys over there use kilometers? 8000 miles is 12874 kilometers.
 

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I've been running the iridium NGKs for 7-8000 miles. It runs great and I gained a little bit of fuel mileage. You have to gap them larger than regular plugs or they can actually hurt performance.
What Iridium's are you running? There's no direct crossover from the CPR9EA9 to an iridium equivalent that I have found yet.
 

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NGK doesnt recommend this. The put an anti-seize coating on them and it is one-time use.

I reckon if you pull the plug out and there is no obvious erosion of the tip, put them back in.
Put a small amount of chain spray on the threads and tighten the gasket down flat, then it won't loosen up or lose electrical grounding.
The chain spray means you can get the plugs out next time as well.
 
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