What up my dudes! So I’m about to check my valve clearance and change my plugs and coolant. Trying to get everything together for the job. The manual says it takes ngk’s the cr8eh-9 or cr9eh-9 if you really push your bike. I’m searching amazon found the plugs I want, but amazon says they don’t fit. I wanted to get the experts to verify they will fit before purchase.

CR8eh-9 in my bike.

The manual says in terms of NGK plugs, CR8EH-9 is the standard heat range fitment.
The CR9EH-9 is one heat range cooler than the 8EH, and unless the engine is in a continuous high range of power output level, the cooler plugs are not only of no advantage, but will be more prone to fouling in normal driving.
CR9EHs will fit, of that there is no question, as the only difference between between it and the 8EH is the heat range.
Keep in mind that the 919 essentially has a "car like engine".
The bhp/litre is not even approaching a high value, and the engine is water cooled - not air cooled.
Generally speaking, unless an engine's output has been increased at least 10% from original design, spark plug heat range doesn't even need to be looked at - trusting the original plug spec was correct for the engine its original condition.

Great info guys! So if I got a high flow air filter and a slip-on would that be enough to change to the colder plugs? I want my bike to run well, but I don’t want a PC3.

Such changes are nowhere near what's needed to justify changing the heat range of the plugs.

Cool cool! Thanks.

What if I put on a Turbo with thicker gaskets and water injection and ran methanol?

Are you like the wrist twisters designated smart ass? Lol.

Way worse. I actually already know everything, but sit back and let others waste their time so I don't have to.

Why comment then? As a fellow smart ass I’m genuinely curious.

Not to sway too much off topic, I'm about to replace my plugs as well, and my concern revolves around SP #3. How the heck do you get to it?

Thanks in advance for response from those in the know.

Cheers,
Devin

I found the most effective tool to be bitchin' & swearin'. I moved the ignition coil...or coils...can't remember if needed to move 1 or 2. I used the 919 took kit spark plug wrench because people here said to. It says replace plugs at 16,000 miles but I waited until 21,000 miles. The tool worked but based on how the plugs looked at 21,000 miles I see no reason to ever do it again.

Yeah Bryce is right. Get the 919 spark plug tool. It will reach down there and allow you to remove it. It also holds onto the plug allowing you to lift and lower it back in.

I just replace the plugs when doing the valve clearance checks (16K miles). Here is how easy #3 is:

Mike, I like that ratchet flex handle tool thingy your using.

A hinged ratcheting box end combination wrench.
Slik bit o' kit.

Well, shoot. Don't have that many miles on it to go that far, and frankly probably don't have to do the spark plug replacement at this point, considering what this thread contains. But now I know for the future. And But....now I'm ready for the summer. Slice of heaven to get this girl back on the road this weekend. Cheers to all!

Devin

Hey guys! Was curious anyone know if ebc makes a rear rotor for the 919? If so were can I get it?

New OEM
Used from a reputable wrecker.
EBC has a listing for round and eyebrowed.
No doubt others do to.
Be careful on correct fit, 919 rotor is bigger than 900!
A 919 caliper will not work on a 900 rotor!
You need all 919 or all 900, mounting bracket included.
A 900 rotor, caliper and bracket will fit a 919.

this thread inspired me to change my spark plugs the other day, and I must say it's one of the best things I have done to my bike so far.

I put the correct heat range(8) of ngk irridium plugs in(for some reason they were cheaper than the standard ngk's) and my bike runs like never before. smoother acceleration, no more vibration over 5k rpm and even the exhaust sounds different.

now I have no idea if I had a problem plug or if the iridium made this difference. the bike has 43 000 kms and I am unsure if the plugs were ever changed, I assume they were at some point. All the old plugs looked good, no sign of fouling or wear on any of them(pic at bottom).

just thought I would share

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Can you link me the plugs you used? My bike is at 43k miles and my bike averages 25-30 mpg.. so i think it's time for new ones. Bike is also down a little bit on power and I'm trying to figure out what's causing it

Damn Quad. That plug looks nasty.

these are the plugs I put in.

NGK CR8EHIX-9 Iridium IX Spark Plug https://www.amazon.ca/dp/B001RLRYGO/..._NQajBbC2S4DMN

I didnt actually get them from Amazon. I got them through work, still don't understand why they were cheaper, but it made my decision easy 😉

see that's kind of funny cuz I'm an automotive technician and if I pulled that out a a car I would think it was in great shape after potentially 15 years

Echo that!

If you were going to put your bike on a Dyno, hoping for the best numbers, Would you put those 15 year old, 42,000 mile plugs in, or would you put a new set in?

Has hp ever gone down with a new set of plugs?

Gosh, is that a test question ?
Correctly gapped new ones for sure ! LoL

I guess my point was more that: I don't know whether the hp gain was more from using the irridium plugs than that of using the standard plugs, because I didnt see an obvious failure, and it's not like the bike was running as if it had an obvious spark plug failure.

Either way I am happy

My assumption is that the the gain would be from the plugs being new, and not the type.
Used plugs can easily give the appearance of being OK, yet not make peak power and do so without any obvious indicators.
Fresh conventional plugs should make the same power as any of the noble metal based small centre electrode plugs.
First it was Platinum, then came Palladium, and nowadays Iridium is the big thing.
Iridium is related to Platinum.
Platinum and Palladium are also excellent catalyst materials, in addition to being very corrosion resistant.
Iridium has excellent corrosion resistance, even in extreme temperature environments.
Hence its use in spark plugs for the centre electrode.
It's a great choice if one wants a 100,000 mile plug as part of being able to maintain allowable tailpipe emissions after years of use.

There was one other noticeable difference between the irridium and standard plugs.

The irridium plug also had the edges shaved off of the bottom electrode. Would this make a noticeable difference? I doubt it, but possible I guess.

On all four corners of the bent rectangular wire?
For its full length?
How about the end profile?
There too?

Hmmm,
I just went into my shop and looked at a spare set of new NGK platinums I have for a previous car.
The ground electrode is a bit thinner than a conventional.
The ground electrode is significantly beveled on the inside edges.
I'll be honest, I don't know what the design intent is.
If I was to guess, I'd have to wonder if it might be an effort to reducer the corner temps because of the thinner section, and/or try to better manage the spark path over the life of the plug.
Thanks for mentioning it, you've piqued my curiosity!

I wish I had taken a pic of the tip now. but yeah it was basically a 45 degree angle on both corners of the ground electrode. making more of a rounded tip. possibly getting a cleaner burn.