Do spark plugs really go bad? (Ponderment)

[dingdong]

We hear advice and read about replacing spark plugs in so many threads regarding poor running engines, high speed misfiring, low speed hesitation, left bank not firing, #3 cylinder not firing and the list goes on..........Well I wonder how many times spark plugs have been purchased and installed for these multitude of symptoms without success??? In almost all cases, in threads regarding above symptoms, someone asks, have you replaced your plugs?

Personally I literally have never ever experienced a truly bad plug. Granted the plug or plugs may not have been firing but in each and every case it was some other problem that caused the plugs to misfire and the symptoms returned.

I admit that I am as guilty as everyone else of replacing plugs hoping to "fix" a problem but every time the symptoms return after 2 miles, or 3 days. What say you?

I'm so bored today! Is it Christmas yet?

[DenverWinger]

After 40-60 K miles I MIGHT notice a slight improvement in performance or cold starting by changing plugs, I've never had a plug "Up-and-Quit" on me unless it was seriously fouled for whatever reason, and it would work fine again after being cleaned..... One would think just re-gapping a non-resistor plug to spec would restore it to "New", save for possible combustion deposit buildup between the insulator and shell, but I can see failure mode possibilities in a resistor plug.....

[AZgl1800]

unless they get fouled up badly, never had to change one.

simpler to put in a new plug, than to clean the old one.

with Fuel Injected engines, rarely will you be able to tell the difference.
the tips wear down a bit, and the gap changes slightly.

My Suburban had 221,000 miles on it when I bought.
Ran "okay" with a slight bit of "weak power" noted.

Found the spark wires in bad shape, and installed new wire and plugs.
That ended the " slight miss tendency "....

just this past week, I picked it up from my trusty repair shop, the intake manifold gasket was leaking, and the harness to the Nox sendsors was torn up.... the Nox Sensors were fouled up beyond using, so the harness and both Nox sensors replaced....

and the PVC valve was replaced with new hoses...

[DaveO430]

Spark plugs seldom just go bad. Sometimes they get fouled which isn't the fault of the plug. I have seen 1 spark plug actually worn out in a 1 cylinder motorcycle , the electrode worn off to up inside the porcelain, but it still ran. All the bad spark plugs I have seen were bad when new, probably had been dropped and cracked.

[WingAdmin]

The primary cause of actual plug failure that I've seen is cracking and failing of the insulation. This can be caused by a few different things:

- Detonation - wrong fuel, wrong timing
- Deposits - oil or other deposits on the plug cause it to heat up. The center electrode expands from the heat and cracks the insulation
- Wrong heat range: Plug is not designed for the heat it is being exposed to, center electrode expands and cracks the insulation
- Engine overheating - center electrode expands and cracks the insulation
- Improper installation - plug too tight or too loose, heat can't dissipate, center electrode expands and cracks the insulation

It's important that the plug be of the correct temperature for the application. Fortunately for our bikes, we have an NGK spec plug that fits pretty much all operational temperatures you're likely to encounter, because our engines stay at a fairly consistent temperature (due to water cooling). Air cooled engines are a different story.

[ekvh]

I have had 2-3 bad NGK plugs straight from the box. If I suspect one of going bad, I swap it and see if the miss follows the plug.

[ct1500]

We hear advice and read about replacing spark plugs in so many threads regarding poor running engines, high speed misfiring, low speed hesitation, left bank not firing, #3 cylinder not firing and the list goes on..........Well I wonder how many times spark plugs have been purchased and installed for these multitude of symptoms without success??? In almost all cases, in threads regarding above symptoms, someone asks, have you replaced your plugs?

Because the 1500 has carbs with a manual (user controlled) choke system many will leave it on for too long which turn plugs black and can partially foul them which gets difficult for the engine to burn off. Think lots of cold starts during the winter to keep it primed for summer. Spark plug construction has come a long way with the exotic metals used unlike when I started working in Dealerships with 30K tune up intervals recommended. Spark plug condition is still one of the best indicators of how each cylinder is running. Modern vehicles have a computer which tells the owner when things are amiss with an engine so there is generally no need to inspect a spark plug anymore.

I may ask folks if plugs were changed to gauge their determination and mechanical aptitude, many will buy a 30 year old motorcycle and start adding LED lights before doing basic work like plugs and filters.

Personally I literally have never ever experienced a truly bad plug. Granted the plug or plugs may not have been firing but in each and every case it was some other problem that caused the plugs to misfire and the symptoms returned.

Fouled plugs would be the primary failure on the 1500 but if you have been around you find loose ones not seated and also some that are cross threaded screwed in a turn and a half in addition to a cracked porcelain from an improper install.

I admit that I am as guilty as everyone else of replacing plugs hoping to "fix" a problem but every time the symptoms return after 2 miles, or 3 days. What say you?

The improper firing of a spark plug is generally a symptom of something else wrong. I do not want 30yr old plugs with a 100K on them with an out of spec gap when they are so easy to change, would you? 40K is about when you can see some wear starting on the NGK electrodes. Common sense and preventive maintenance dictates if taking a plug out then replace it if unknown when they were previously done or just go ahead and keep installing more lights and the leather grip tassels .

[detdrbuzzard]

when I got my 1500 wing it had close to 40,000 miles on it. I changed sparkplugs at70,000 miles. the Mighty ST1300 had 25,151 miles on it and I think I changed plugs at 50,000 miles. I did not notice any change in performance or ease of starting on either bike

[Terry D]

Spark plugs wear out but they don't go bad until you can no longer achieve the proper gap. Now, let me back up a bit. I did have a sparkplug in a Chevy V-8 that the white porcelain blew out of the metal part and was still attached to the plug wire. But that was a stock AC plug back in 1966.

[dnehasert]

I bought an 82 GL1100 some years ago and it ran well but wouldn't much over 70 mph. Finally changed plugs and then ran great. Had about 70,000miles on it when I bought .

[Asphaltmaniac]

I clean and re-gap mine at the beginning of the 2nd year after installation. The next year I get new. I believe the vehicles going 100K with out a plug change are platinum tipped.

[gervais]

well

i dont beleive that you "must" change the plug between 4 and 8 000 milles .
NGK are the best plug for japanese engine and as someone wrote ,since its a water cool there are chances that the life of the spark will be + more + .

i just changed on my Highlander,234000 km,iridium and baught THE SAME plug.
Playing with spark plug replacement demands knowledge that many dont have so dont play and use OEM number .

i remember my years of ice racing on bikes and some plyed with their plug,,most of the time it finished with a beautiful hole on the piston.


Hey Great 2019 all,
Ride safe and keep smiling as they say.

Gervais

[Scott_MacMartin]

Spark Plugs
78,575km - the original plugs are the correct colour, but are gapped at 51~53 thou. New Autolite Platinum AP3923 plugs are installed, with a gap of ~35 thou. When the engine is idled after installation, I note a solid idle - the previous idle had an occasional miss which I had forgotten was not normal.

162,000km- the autolite AP3923 plugs are removed, and replaced with NGK BKR6EGP plugs. GP means a platinum plug. New plug gap not measured. (Internet 2016 suggests BKR6EGP plugs are gapped at 35 from the factory.) Old plugs AP3923 now have a gap of 47 thou.

239,240km - The old plugs are removed with ease. New plugs BKR6EIX 11 installed. Finger tight and then just more than half a turn to install properly. Old plugs seem good colour and have a gap of 44 thou.

(80,000 km is the same as 50,000 miles)

No failures and I suppose that I could have just re-gapped.

[offcenter]

I seem to remember replacing plugs 50 years ago because they did go bad.
Electrodes would burn away or insulators would break down.
But I'm guessing that the quality of modern plugs has increased dramatically.
The original plugs in my Toyota pickup truck lasted about 160,000 miles.
That never would have happened years ago.

[dirtwinger]

Many years ago, when platinum tip plugs were first introduced and touted to "last forever," I put them, at the recommendation of the auto parts guy, into my Honda 350. The result was melted platinum tips that introduced very bad performance in short order. A free replacement set of the same plugs produced the same result. That was quite convincing. A return to the original equipment plugs made everything okay again. So much for the foray into modern plug technology!

[tinwacker]

my friends 2002 with 40 thousand on it was running bad so I changed the plugs and that fixed it
The plugs did not look bad except for a seadie look at the flat below the treads, He is not an aggressive driver so I assume it was a little carbon but not real sure It does run like new Now.

[bellboy40]

I bought a GL1200 LTD new and rode it for over 70k miles before replacing the spark plugs. They still looked good and I didn't notice any difference in either performance or fuel mileage. When I got my 1500, it had about 25k miles on it and I went ahead and replaced the plugs just because. They now have about 40k miles on them and the bike still runs very well and mileage is around 40+ mpg. As others have already experienced, I have never found a bad plug in any vehicle I have owned, even though I have replaced a lot of plugs over the years.

[winguyjo]

i don't have that much experience with motorcycles, but have overhauled dozens and dozens of lawn mowers, chain saws, and weed wackers.
bad plugs are rare, but they do happen. could be that the few bad ones i have come across might have been refreshed with a good cleaning, but it's not worth the bother as i have many good (used) ones to choose from.

having said that, i once was desperate to buy an old work van on a sunday so that i could use it on monday. found one that was running, driveable and dirt cheap so i went for it. it was a bit hard to start during the pre-purchase inspection and the next day it was even more difficult to start, eventually not starting at all around mid-day. got towed to a shop, they fixed it and showed me the 8 spark plugs that they had removed. there were 3 or 4 different brands and 2 or 3 of them had virtually no side electrode left.

conclusions reached : plugs do go bad and previous owners are nutjobs.

[wallyos]

I have never had a spark plug go bad (fail) in 54 years. When I was road racing on the 70's I fouled them because the heat range was too cold and holed a piston by using too hot a plug range. We almost always had a Champion spark plug Tech at the track and he taught us a lot.
The GW is a mildly tuned engine and the factory spec'd plugs are perfect, but they do "wear out". When you examine an old plug, use a magnifying glass. Compare the center electrode to that of a new plug. It should have sharp edges on it an not at all rounded. The same is true for the side electrode ------ sharp edges.
A high voltage charge will jump a gap far more easily between sharp edges than between rounded electrodes This produces a hotter spark for more complete combustion and produces better mileage.
Honda recommends 40000 miles replacement for the NGK standard plug (DPR7EA-9) under normal riding conditions. Examine them per above and replace as necessary. The harder you drive, the sooner you may have to to replace them.

If you want to go 100000 miles then use NGK Iridium tipped plug (DPR7EIX-9). They are the same heat range (DPR7) Except the center electrode is made of iridium which does not burn away as easily as the standard metal. The center electrode is also has a needle point which stays relatively sharp as it wears (burns) away over time.

NGK link below:

https://www.ngksparkplugs.ca/results-mo ... Motorcycle

[keithg64]

I just always figured that with my maintenance schedule I'll change plugs every year but I'll usually ride about 15k-18k miles a year. Along with everything else, plugs are cheap enough.

[mludlow]

This might be my first post. I've been reading this forum for years but have not had anything to add but thanks to all for helping me.

A few years ago I had a vehicle which seemed like the transmission was slipping. It had about 60,000 miles on it. This would happen when cruising at 45 MPH or so then lightly loaded, say from an incline. The car would falter and downshift kind simultaneously. The RPMs seemed to rev freely then clunk into a gear. I thought the transmission was going. There were no trouble codes recorded. I was not about to have the transmission replaced and started looking for a new car.
I searched the internet for a solution while it slowly got worse over a few months. After many attempts I finally stumbled across a comment from a mechanic that made some sense to me. He said that under load you can experience a misfire or short series of them but the computer will delete the error code it if it does not repeat, and that this could be caused by bad plugs. I knew that weak spark would cause a miss when an engine is loaded.
I checked the front three spark plugs and found the gaps to be .090-.100" instead of .060". I had never seen plugs that worn before. I changed those plugs and the back three which meant removing the intake manifold for access. The car ran and shifted like new. The recommended change interval was 100,000 miles.
Replacing the plugs saved me from buying a new car for 4 more years.

[maxm-01]

My 05 Wing has spent most of her life in the 80 to 95 mph range. She starts right up, never coughs, no high speed miss (100 mph and higher) and she is sneaking up on 132,000 miles. So my experience says nope they don't go bad. Even on my 95 Wing I only replaced the plugs once, and that was only to make me feel better, retired her after 200,000 miles.

[winguyjo]

[tinwacker]

My friends 2002 GL 1800 with about 40 thousand on it started to run bad, We added injector cleaner to it with no luck, Changed the plugs and it runs great now, Plugs had a seedy look to the end where the flat part below the treads are, H]Dark in color but not sooty , All is good now

[AZgl1800]

My friends 2002 GL 1800 with about 40 thousand on it started to run bad, We added injector cleaner to it with no luck, Changed the plugs and it runs great now, Plugs had a seedy look to the end where the flat part below the treads are, H]Dark in color but not sooty , All is good now

I fully suspect that is because he was using junk gasoline, and especially the E-10 crap.

my 2002 with 114,000 miles runs like brand new, has had 1 set of spark plugs installed by a previous owner ( I have the records ). I always buy Pure Gas when it is available, which it is here in my state.

this picture shows the results of improper fuel burn, from bad fuel/air mixture.