Spark Plugs

[FJRoss]

Wondering what people are using these days for plugs for Gen I and Gen II bikes? And how often are you changing them?

The designated plug is an NGK CR8E and the change interval is given as 8,000 miles or 13,000 kilometers, according to my owners manual. I have never changed them anywhere near that often and after letting them go more than twice that distance, I never noticed especially great wear or a performance difference after changing. (Usually change when doing a valve check and not in between.)

I have also used the NGK CR8EIX iridium plugs and have let them go as much as maybe 40,000 miles. Again, no issues. I ended out by changing them "just because".

Anyone using a different brand or type? What is your change interval?
Anyone ever have a plug fail?

Doing a valve check in the next week or two and thought I would see if anyone is doing anything differently from what I have done in the past. The NGK CR8EIX iridium plugs in the bike have been there for over 60,000 km and I am debating just leaving them. (Might wait to see how they look.)

I have an "old" set of CR8EIX that I took out a number of years ago - kept them around for spares from my old bike. Kept them because they still looked almost new. Probably should toss them.

I know the Gen III+ take a different plug...

[ionbeam]

A few things in no particular order.

The Gen I & II have a waste spark system. There are two coil packs with two plug wires each. One wire will cause the spark plug to fire from the center electrode to the side strap electrode (ground); the other plug will fire from the side strap to the center electrode. You can swap these pairs of spark plugs around to double the plug life. One plug wire will be positive several thousand volts and the other plug electrode will be negative voltage at several thousand volts.

The Gen III and up have a 'coil over' system where each plug has its own coil and they are fired only on the power stroke. This will help the plug last longer.

With any modern engine that has fuel injection and electronic ignition you can run the plugs until they are beyond whipped and the engine will still run ok, start ok and not take a big hit to gas mileage. One reason you may want to pull and/or change spark plugs is because of carbon buildup at the threads. If carbon builds up it can freeze the plug in or damage the cylinder head threads when the hard carbon cuts threads on the way out. The FJR seems to be resistant to carbon buildup.

As a spark plug ages it starts to erode the center electrode and to a lesser extent the side electrode. This causes the plug gap to widen over time. As the gap widens it becomes harder to initiate a spark. Additionally, the coil voltage will start to go up as the plug becomes harder to fire. If you have any compromise to the high voltage system you can start to get high voltage leaking to ground. Again, the FJR OEM parts seem to be resistant to this kind of failure.

High voltage likes sharp edges, sharp edges give the very best point to initiate a spark. As the edges erode and become rounder it becomes harder to initiate a spark. Modern electronic high voltage systems make so much more voltage than the old breaker point systems that the electronic system is more capable of firing a worn plug with a hot blue spark.

NGK iridium spark plugs have a small, pointy electrode that makes it easier to initiate a spark. It needs to be iridium to keep from quickly burning up the electrode. Iridium spark plugs are 'better than they need to be' for the FJR so you will not really get much of a return on your investment.

So, when do you need to replace your spark plugs?

The picture of a spark plug below is a how a brand new plug looks. The critical things to see are the center electrode and the side electrode. Notice that the center electrode tip has a sharp 90° edge, absolutely no rounding. The side electrode has two sharp corners and the entire edge that faces the electrode has sharp edges. As the plug wears the spark initiation point can wander around the center electrode and wander around the side electrode.



In the picture below is a really, really worn spark plug, but it illustrates what a worn spark plug looks like. The center electrode is completely rounded and so are the edges of the side electrode. You should change spark plugs long before they look like this. Ideally, when you pull a spark plug you should inspect the electrodes using some type of magnification. Under magnification, when you start to see rounding completely around either electrode it's getting time to replace the spark plugs.



Changing plugs every 8k miles is ridiculous. Inspect your plugs when you have a valve check, maybe replace them then because they are already out. Don't expect to notice any difference when they are changed.

[FJRoss]

Thanks ion
Pretty much as I have been doing. Maybe I should just swap around the iridium plugs that are in there. Will have a close look. Especially the side electrode. Would you expect problems with a set of iridium plugs that were removed after maybe 10,000 mi. and just sat around for a number of years? Didn't know if they might degrade - wouldn't expect so unless there was corrosion at the side electrode, crush washer or threads. I assume moisture absorption into ceramic isn't an issue

[ionbeam]

As long as you don't drop the plugs they they should last forever on a shelf. There is only a resistive core inside the plug between the cap and the center electrode. The ceramic around the electrode in the tip can't be chipped or cracked which is sometimes a problem with iridium plugs. The ceramic around the tip electrode seals the plug core and the metal shell with the side electrode.

In a stock FJR just about any brand of plug that meets OEM specifications will work, without one brand performing better than another. The only way one plug brand could be better than another is wear resistance of the electrode and side electrode. There will be no performance difference.

The only true guide as to when to replace plugs is by looking for rounded edges completely around the electrodes.

Swapping plugs #1 & #3 (coil 1) and plugs #2 and #4 (coil 2) will get you closer to doubling plug life.

[raYzerman]

Another excellent ionbeam summary, my sentiments exactly... I'll add a couple of real world things from working on so many FJR's and reading what others have had issues with.

There is a possibility of carbon build-up on the first 2-3 threads as carbon wicks up. Risk is damaging threads upon removal and I know of two who snapped off the nut part of the plug leaving the threaded part in there (ouch, almost impossible, very rare!). A couple others had difficult removals and oops stripped aluminum threads. You'll hate yourself when it happens, so simply prevent it. My recommendation, remove plugs at say 25k miles, er sumthin like that, brush off that carbon if Iridium, replace if standard, why not. Optional, a light smear of anti-seize on the first 2-3 threads only... works fine, no worries about proper grounding.

Ignore Yamaha torque spec., follow plug manufacturer's recommendation, hand install, tighten 1/4-1/2 turn more, crush washer will not be fully crushed but adequately torqued, and leaves you more "crush" for second install, say in the case of Iridiums you tend to leave in longer.

Look at your old Iridiums, if it looks like they are running a tad hot, drop down a heat range, i.e, CR9EIX. As for Iridiums, I use them "just because" after I feel the originals should be replaced (around 25k, "just because").

As for Gen3/4, projected tip plugs means electrode a tad deeper into combustion chamber... can you say Euro4 emissions.. if you do your homework, there has been no change in cylinder head casting part numbers, dimensionally the same. I use CR9EIX in those, can use CR8EIX if you choose, no worries. Not sure if using standard plugs would I get the projected tip (in the past, they have been hard to find, especially the Iridiums).

[raYzerman]

Note added, Gen3/4's coil over system also has unique ignition trigger wheel and ignition pickup under the right side timing cover. Not interchangeable with prior Gens. Obviously, different ECU to deal with that... can you say Euro4?

[FJRoss]

As per the great advice from Alan and Ray, I'll have a good look at the plugs and make sure the bottom threads aren't carboned up. I haven't had issues with this in the past but worth a check. Might re-use them or go with the "old" used set that have been sitting around the garage for a number of years.

I will have a good look at the electrode edges under a magnifier.

[Pterodactyl]

Damn Ross..... you ask a simple question and get a doctoral level lesson; presented in a simple, direct and easy to understand manner..... and with pictures.

[SkooterG]

After numerous FJRs and umpteen billion miles what I have found works for me is kind of what the fart smellers talk about.

In the very beginning, I changed at the 8k interval. What a joke! When I extended the interval, I went to Iridium.

Now, I simply change the plugs when I do a valve check. From experience I have extended the valve check interval to 30-35k miles. Now I only use standard plugs and they look fine after 30-35k miles. Not anything like ionbeam's 'bad' photo. This is also the only time I change the coolant.

So at 30-35k valve check, new standard plugs and new coolant. KISS.

[FJRoss]

Now, I simply change the plugs when I do a valve check. From experience I have extended the valve check interval to 30-35k miles. Now I only use standard plugs and they look fine after 30-35k miles.

That is what I did the last couple valve checks on my '07. Just threw the question out there because the previous owner of my 2011 put the iridium plugs in just a little before I bought it. I think I will have a close look at them when they come out and either swap them around as per ionbeam or just go back to the old CR8E standard plugs with a change when I do the valve check.

(I also do the coolant with the valve check. Absolutely no need to do it more frequently.)

[rbentnail]

After numerous FJRs and umpteen billion miles what I have found works for me is kind of what the fart smellers talk about.

In the very beginning, I changed at the 8k interval. What a joke! When I extended the interval, I went to Iridium.

Now, I simply change the plugs when I do a valve check. From experience I have extended the valve check interval to 30-35k miles. Now I only use standard plugs and they look fine after 30-35k miles. Not anything like ionbeam's 'bad' photo. This is also the only time I change the coolant.

So at 30-35k valve check, new standard plugs and new coolant. KISS.

I've always used plain ol' NGK CR8E plugs and found them to be perfectly fine for at least 30K miles. Basically I change them when I have them out for a valve check. This year will be different- I haven't replaced them in 2 or 3 yrs and I got Ivan's flash so for the feel-good factor I bought the Iridiums. There's a first time for everything!

I'd never consider putting used plugs back in. At approx. $4 each new, what for?

[Powerman]

If I have the tank off I pull the plugs and put in a spare set. I put those in the spark plug cleaner to clean the carbon off, check the gap and they become spares. Quick check under the hood.

I had a guy with three stripped plug hole threads like Ray said, put inserts in all four holes. Had to clean the carbon off pistons, great maintenance.

95% of engines don't really need high tech sparking. I wasted money on " cool stuff ".

[FJRoss]

I have the iridiums that are in there now and a set I pulled some time ago and never threw out. I put the old set under a magnifier and two of them were clearly better than the other two, as ionbeam suggested because of the way the FJR ignition works. I'll have a close look at the other set of iridium plugs when I do the valve check but will put in the CR8E set I bought. Might keep the best four iridium plugs for spares. No crusty carbon buildup on the threads of these ones.

[HotRodZilla]

I have the iridiums that are in there now and a set I pulled some time ago and never threw out. I put the old set under a magnifier and two of them were clearly better than the other two, as ionbeam suggested because of the way the FJR ignition works. I'll have a close look at the other set of iridium plugs when I do the valve check but will put in the CR8E set I bought. Might keep the best four iridium plugs for spares. No crusty carbon buildup on the threads of these ones.

No ide why, but unlike others, my bike is very sensitive to the OEM plugs going past 8k miles. I get a quality vibration that goes away the second I swap the plugs. They were so cheap I never swapped them back and forth.

After a few plug changes, I went to iridium plugs and they have been there a long time. I should pull them out and replace them, but the bike runs great and I'm not quite to a valve check. Maybe I'll have them changed then, as I do not do my own valve checks, but I do have another set of plugs here. Actually, I got this set from Petey a few years ago.

[FJRoss]

Never had an issue that I could attribute to plug condition. I have mostly used iridium plugs and usually changed them with valve checks. I have also run standard CR8E from one valve check to the next and they did not look terrible when they came out. That was all in 185,000 miles on my '07. Haven't had anything other than the iridiums in the '11 - were in it when I bought it.

Doing the valve check in the next couple of weeks. Might clean throttle bodies at the same time - I don't think they have been done. Hoping that I don't need to reshim - about 80,000 miles on the bike now. This is only the second check AFAIK - original owner didn't have to change anything on the first go around.