Plug Question

I am prepared to accept abuse. I just got off my 05. It has 10,043 miles on it. It still has a bit of tread on the original Metzlers. Yeah, I know, I am not riding it right. (yes, I have feathers) I did buy some NGK Iridium plugs at 8000 miles. They are still in the box. Is there really any reason to change them if the machine is averaging 47 mpg and running perfectly? :blink:

Just Plain Dave said:

I am prepared to accept abuse. I just got off my 05. It has 10,043 miles on it. It still has a bit of tread on the original Metzlers. Yeah, I know, I am not riding it right. (yes, I have feathers) I did buy some NGK Iridium plugs at 8000 miles. They are still in the box. Is there really any reason to change them if the machine is averaging 47 mpg and running perfectly? :blink:

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Nope. Skootfucious say, if ibike running fine, leave alone. Just crash it, put arm in sling, mope about house.

Thanks TWN, I knew you'd be there for me.....

I waited til about then before changing the plugs. Bike ran fine, mileage fine. But when I pulled the old plugs, I was a little surprised at the wear. There was a visible gap difference. I don't exactly know what that means to the engine, but just testimony to the fact that wear was significant.

The plugs are fine. So is the tire wear. Do yourself a favor though and pull the air cleaner out and blow it off or change it if you feel it's dirty enough. Trust me, there's enough dirt to make a difference by now.

OCfjr said:

The plugs are fine. So is the tire wear. Do yourself a favor though and pull the air cleaner out and blow it off or change it if you feel it's dirty enough. Trust me, there's enough dirt to make a difference by now.

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Naahhhh, air is still able to go through it! Why mess with it? Wait till you have to use wide open throttle for it to idle, then clean or replace it. As far as the plugs, wait until......when? Misfire? No start? Coil failure? Plz, when does one determine at what point to change these out? I'm very curious on this one, at what point is it time, and what precipitates the moment?

Truf be told, I'm with rad... not as anal a schedule mind you, but everything I do except the tires is on a 4K, or multiple thereof, cycle. My plugs go at 12K, whether they need it or not and I do a TBS at that point, too. Sumpin' to be said for not scrimping on the consumables, I suppose.

Folks need to realize this isn't granny's Buick V6. This is a high perf motor, on a par with race motors just 20 years ago. When the sharp edges of the center electrode are rounded, performance suffers. This is why the trend toward platinum plugs-the platinum resists the erosion that renders a plug ineffective. Look at this well worn plug, you can easily see how the center is rounded.



Spark likes to jump from sharp edges, arcing erodes these edges, making the spark efficiency drop. Late spark means timing changes, large gaps (from same erosion) means timing changes and coil stress. Both contribute to less than optimal firing. Engines, even with all the advances in ignition, still respond to a fresh set of plugs by running smoother, more powerfully, more economically. While much has changed over the years, that hasn't.

I'm not denying Radman's well respected opinion, just saying 10k is ealier than I would change them. I did mine at 16k, (I like multiples of 8 ). I put in Iriduim plugs. I notice mileage suffering from a dirty air filter long before spark plugs. I'm guilty of letting that go too long once. :guiltysmiley:

I'll give anyone $20, (or that value in beer), if they can pull a plug from their FJR that looks anything close to Rad's picture example above. EFI motors simply don't get that far off in most cases. Sure, electrode wear occurs! But most people can't read plugs on EFI motors like you could in the old days on carb'd motors.

With O2 sensors and closed loop tuning, along with all the other sensors used in modern engines, things are far better tuned than they used to be. One result of that, IMHO, is less pronounced spark plug wear.

But what the heck do I know, I can't feel how much faster my bike is with a carbon fiber fender extender on it, even though everyone knows carbon fiber makes a bike faster. :lol:

I thought it was that internal resistance builds up in the plug because they're fired twice as often as cars and that the computer and ignition can compensate to an extent, but the more miles the harder it is for to compensate.

Had a 2005 Crown Vic squad in the shop, 29 thou on the odo, poor running complaint. Started good, no codes . Tech cleaned IAC, replaced fuel filter (problem on these, big problem generator), checked and replaced EGR, then the EGR controller, cleaned the throttle body. Car left running good. Next day or two, back again. Running like crap. Sent to Ford. Thorough scan, several components replaced as test, problem remained,intermittent, writeup showed a lot of head scratching. A call to Ford tech line, and 8 Motorcraft sparkplugs later, a fine running automobile. These are high dollar double platinum plugs, mind you, last forever. Not. Leave 'em in forever, fine by me. Frank gets them twice a year, or every 6-8 thou, also Iridiums. Frank loves my ass, and runs top notch day in, day out, while I try and counter skeptics, and advise those here who have no starts etc. Oh well.........

radman said:

<snip> Frank gets them twice a year, or every 6-8 thou, also Iridiums. Frank loves my ass, and runs top notch day in, day out, while I try and counter skeptics, and advise those here who have no starts etc. Oh well.........

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Question Oh Exhalted Radness - If you change them every 6-8k, why the Iridiums?

Frank gets the best I can find, in every way. My toy, my only toy now, so it's affordable. The iridiums hold the tune longer, long life works in the short as well as the long run. I get them for a good price, being in the business, but would follow the same change cycle even if I couldn't.

radman said:

Frank gets the best I can find, in every way. My toy, my only toy now, so it's affordable. The iridiums hold the tune longer, long life works in the short as well as the long run. I get them for a good price, being in the business, but would follow the same change cycle even if I couldn't.

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They "hold the tune longer", but you change them at the same interval you would plain jane plugs? :blink: :blink: Err, Ok Rad, thanks for playing.

I respect your experience Rad, but mine's different from yours. I don't toss perfectly good parts away. Spark plugs are the most over replaced parts on a vehicle, IMHO. If you can tell the difference between 8k Iridium plugs and new ones, kudos to you my friend. :good:

I once owned a Toyota Supra (great car, imo) with an in-line DOHC six. While showing it off (under-hood) to a machinist friend; he noticed the factory decal on the rad header-panel, "this vehicle is equipped with fine-wire electrode (like Iridium) spark plugs -- Toyota recommends they should be inspected every 60,000 miles." My friend said, "Well, you can throw-away your spark plug wrench."

Seriously, most cars don't have (or, didn't used to have) the *wasted spark* ignition system that most motorcycles use -- and, is the cause for more rapid plug wear (twice the spark incidents). Truth be told, I can't remember if the Supra had wasted-spark, or not -- but, some cars do (engines that have computer-controlled coil-packs often use the same wasted-spark system).

I don't see spark plugs as big volume sellers anymore.... they sure used to be tho. :blink:

Just Plain Dave said:

It has 10,043 miles on it. I did buy some NGK Iridium plugs at 8000 miles. They are still in the box. Is there really any reason to change them if the machine is averaging 47 mpg and running perfectly? :blink:

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Change the plugs now. Put the Iridiums in.

Then change those out somewhere 16,000 miles later.

The OEM plugs are absolutely one of many areas that Yamaha performed some "cost-savings" initiative. They are crap, garden-variety plugs that you would typically put in your lawn mower. There's a reason Yammy recommends 8K intervals for those plugs.

But you can easily go 16,000+ miles with the Iridiums. That is the reason to go with them: longevity.

Alternatively, you can follow some of the fucked-up advice you've read in this thread. Your bike; your choice.

Plugs now, while you CAN'T tell that anything is wrong. When you can feel bad plugs, then they are WAY overdue. Sluggish starting is usually the first sign of worn plugs.

Spend the $$$ for Iridium if you wish. NGK also makes an "ES" plug that is an improvement over the "E" and costs only a couple bucks more. But do plugs and TBS at the same time, every time.

It's not so much what plugs you use, as it is how often you do them.

+1 on the air filter recommendation.

The main reason plugs last so long these days has nothing to do with the ignition systems, EFI, PFI, etc.... The reason they last so long is that the fuel does not have lead in it anymore. Lead deposits are what caused the fouling and short plug life. Even the best dual platinum or iridium plugs would foul quickly with leaded fuel. Until lead was eliminated from fuel there was really no need or incentive to develop anything more than the garden variety spark plug since they were replaced so often....and long before they became worn and rounded like the one in Rad's picture. Then again.....you have to be of a certain age to remember leaded fuel.....LOL.

BTW....unleaded fuel is also what makes "reading" the plugs so difficult. An OEM engine running unleaded fuel will have almost perfectly white porceleans even after thousands of miles. And that is running at 14.7:1 which is slightly "rich" at cruise compared to what many are used to with leaded fuel engines of the past.

Certainly the sharp edges are important and a well rounded, worn plug like the one in Rad's picture would not perform nearly as well as a new, sharp, iridium plug. I just cannot imagine a plug, any plug, looking like the one in that picture in only 10,000 miles, though.

I have personally seen countless dual platinum plugs from various manufacturers (including AC, Nippondenso, NGK among others) go 100,000 miles without the first hint of a problem. And that was on an automotive ignition system that DID use the "waste spark" system. In fact, many vehicles on the road do use the waste spark type system that fires the plug every revolution whether it needs to fire or not. Generally, any direct fire system with a plug lead directly from the coil to the spark plug and two plug wires per coil is a direct fire type system that uses waste spark. Practically speaking, on an engine running unleaded fuel, I would expect a dual platinum plug to run virtually forever.

The iridium plugs also show excellent life in automotive testing that I have seen . Without the platinum pad on the ground electrode, however, the gap will wear with time compared to the dual platinum plugs but the wear is still minor and the plugs are capable of 100,000 mile service....in automotive applications.

Bikes typically run about double the RPM at cruise speeds compared to car engines so even cutting the automotive comparisons in half (for double the firing events) the plugs would still go near 50,000 I would expect.

This is why I need to shy away from these discussions. Someone asks advice, I offer what I've learned over 40+ years of wrenching on both street and race machines, reading thousands of tech papers, articles, books, and hands on experience on almost every type of engine known to me. I stay current, I can still polarize a generator, I can still overhaul from memory a 49 Buick Stromberg, set up a SixPack induction system, overhaul and synch a set of 4 CV carbs in an afternoon, but I just can't seem to get past that I believe a motorcycle engine is a high performance machine, and should get treated as such. Where I don't mind running a set of plugs in my Merc engine 30 thousand miles, I just can't imagine doing the same in my FJR. From the moment they're installed, plugs start wearing. Good plugs last longer, the best longer yet, thats why I use them. But always, an engine just tuned deteriorates from the moment it's started. My "fucked up advice" would be to listen to those other guys. They'll save you the $25 my advise would cost you every 8-10 thousand miles. Lord knows it's a hard job, 20 minutes out of ones life can't be recovered, and the $.0025 per mile cost is unlikely to be recovered.