Your thoughts on When to change spark plugs?

[Cobwebs]

Yep. Here ya go.

https://www.google.com/search?q=spar...1e8Pq8W8wAk_30

u tube - how to after the add.

https://www.youtube.com/watch?v=uxNS7teHmpc

But they all seem to state a different reading to look for. One said to consult a mechanic lol! Another said depends on the brand of plug and usage.

[BajaRon]

But they all seem to state a different reading to look for. One said to consult a mechanic lol! Another said depends on the brand of plug and usage.

You can usually find resistance specs for a plug from the manufacturer.

[PMK]

Even if we know the resistance value of a new spark plug, we have no guidelines on what might be an acceptable increase in resistance of a used spark plug.

New coils are $90 each, and requires 3.
As the spark plug resistor breaks down, the loads on the coils increase. At extreme cases, the ignition coil fails even before the spark plug fails. Install a new coil on a worn spark plug, and the failure cycle begins again.

Spark plugs are cheap, coils are costly. Yes the labor can get really expensive too.

In short, there is no true right or wrong answer. Get the best performance and longest expected life from coils by replacing spark plugs at mileage intervals, not visual condition. Or run them until a misfire, and replace plugs and coils. You will likely get a decrease in performance and mpg, but the run them until a misfire is probably most cost effective for those that have a dealer do the work.

[BajaRon]

Something that I didn't mention is that checking the resistance value can identify counterfeit spark plugs as well. And possible headaches down the road.

There is a huge industry dedicated to nothing but counterfeiting products. Spark plugs, batteries, computer memory like SD cards, etc. Even Loctite products are widely counterfeited. It is almost impossible to avoid the counterfeits these days. You really have to know what you're looking for to find them.

[IdahoMtnSpyder]

It is almost impossible to avoid the counterfeits these days. You really have to know what you're looking for to find them.

That was the case already 15 years ago. I got burned by counterfeit Gillette Mach III razor blades. Almost ripped the skin off my face. By the time I needed to use them and discovered they were counterfeit the eBay seller was gone. The tell tale sign was the "Made in XXX" on the package. Interestingly genuine Gillette blades did not have a "Made in ...." note on the package.

About 20 years ago, or more, the US Army had a turret come off a tank because of counterfeit bolts.

[BajaRon]

That was the case already 15 years ago. I got burned by counterfeit Gillette Mach III razor blades. Almost ripped the skin off my face. By the time I needed to use them and discovered they were counterfeit the eBay seller was gone. The tell tale sign was the "Made in XXX" on the package. Interestingly genuine Gillette blades did not have a "Made in ...." note on the package.

About 20 years ago, or more, the US Army had a turret come off a tank because of counterfeit bolts.

Counterfeits probably started as soon as there was a product to sell. So it's not new. It's just gotten to a whole new level. We all deal with it.

[Cobwebs]

You can usually find resistance specs for a plug from the manufacturer.

Couldn't see anything at NGK, only guesstimates of mileage achievable. Might have to contact their white coat department.

[Isopedella]

Dont accept a ..., between yadi ya and mmp. You need the exact measurement. Down to microns.

[Cobwebs]

Dont accept a ..., between yadi ya and mmp. You need the exact measurement. Down to microns.

Down to microns.....................gotcha. Thought I might put a rag over the mouthpiece when I call too. Told 'em I was from Bosch last time and they accused me of industrial espionage
hidesbehindsofa.gif

[BajaRon]

Dont accept a ..., between yadi ya and mmp. You need the exact measurement. Down to microns.

Microns? That's a measurement of distance. I assume you're kidding!

Most resistance spark plugs like what we use in the Spyder are in the 5k~6k oms range. Counterfeit plugs are usually several times this amount. A defective spark plug will also give a much higher reading, or possibly none at all if it has completely failed.

But granted. It's a subject that few ever concern themselves with. When you add the resistance of gap in a heated and compressed atmosphere of an engine cylinder. The resistance of a spark plug is negligible.

[Isopedella]

Microns? That's a measurement of distance. I assume you're kidding!

Yep. Tiny. Down to Micro-Poofteenths. Which is "Some Downunder Stuff" and an accepted and recognized unit of measurement.

Also very much tongue in cheek....

As it appears its being asked for an exact measurement and not a range of acceptable ohms.

[BajaRon]

Yep. Tiny. Down to Micro-Poofteenths. Which is "Some Downunder Stuff" and an accepted and recognized unit of measurement.

Also very much tongue in cheek....

As it appears its being asked for an exact measurement and not a range of acceptable ohms.

I am not well versed on 'Down Under' terminology. But I like Spiders, so you're good with me!

[PMK]

I have replaced many spark plugs due to misfires and engine roughness. This tool in the link is one we use as needed in the aviation industry.
https://www.aircraftspruce.com/catal...empestat5k.php

We also still clean by grit blasting (only the inexpensive massive electrode styles), set plug gaps, and “bomb” test each spark plug to witness proper firing while under pressure. This machine allows that.

https://www.aircraftspruce.com/catal...4aAjVNEALw_wcB

Cheap aircraft spark plugs, massive electrode style with no exotic metals run about $40 per spark plug. Two spark plugs per cylinder, so on a common 4 or 6 cylinder engine, 8 or 12 plugs. Double that for a piston twin engine aircraft.

Those inexpensive spark plugs, depending upon the performance level of the engine, last from 150 hours use to about 500 hours until the electrodes are worn to or beyond acceptable limits.

The high performance spark plugs for aircraft are typically iridium electrodes to reduce wear and erosion. Those spark plugs run about $100 or more per spark plug, depending upon where you get them. So not uncommon to spend $2400 on just spark plugs for a high performance twin.

The expensive spark plugs almost always are replaced from a failed resistor. The electrodes show very little or no wear. Simply use wears out the carbon resistor, rendering the spark plug unable to fire during use. In those cases, the misfire, most times is found early, and worse issues do not arise. In situations where the misfire was allowed to continue (dumb pilot or over water operation), the misfire can ruin the shielded spark plug lead, or even carbon track the magnetos distributor block, causing cross firing a different spark plug / cylinder at the wrong time.

Regarding Spyder spark plugs, they are not expensive. The 1330 uses a COP design, and as spark plugs age, the coils can become overloaded and internally fail. In extreme cases of failing spark plugs with a COP setup, a quality coil will not fail, but the discharge will burn thru the spark plug boot, finding the lazy path to ground, going around the spark plug, since that requires a huge effort with a failed spark plug resistor.

In simple terms, modern technology has given us spark plugs with exotic metals and electrodes that do not wear or erode away. In typical fashion though, the least expensive item in assembling a spark plug is the carbon resistor, and that least expensive item causes the issues.

Old school visually inspecting spark plug wear is no longer an option. Manufacturers test and know expected life of a spark plug before damage occurs to other more expensive items. Modern technology requires modern maintenance. Plugs are cheap.

[BajaRon]

I have replaced many spark plugs due to misfires and engine roughness. This tool in the link is one we use as needed in the aviation industry.
https://www.aircraftspruce.com/catal...empestat5k.php

We also still clean by grit blasting (only the inexpensive massive electrode styles), set plug gaps, and “bomb” test each spark plug to witness proper firing while under pressure. This machine allows that.

https://www.aircraftspruce.com/catal...4aAjVNEALw_wcB

Cheap aircraft spark plugs, massive electrode style with no exotic metals run about $40 per spark plug. Two spark plugs per cylinder, so on a common 4 or 6 cylinder engine, 8 or 12 plugs. Double that for a piston twin engine aircraft.

Those inexpensive spark plugs, depending upon the performance level of the engine, last from 150 hours use to about 500 hours until the electrodes are worn to or beyond acceptable limits.

The high performance spark plugs for aircraft are typically iridium electrodes to reduce wear and erosion. Those spark plugs run about $100 or more per spark plug, depending upon where you get them. So not uncommon to spend $2400 on just spark plugs for a high performance twin.

The expensive spark plugs almost always are replaced from a failed resistor. The electrodes show very little or no wear. Simply use wears out the carbon resistor, rendering the spark plug unable to fire during use. In those cases, the misfire, most times is found early, and worse issues do not arise. In situations where the misfire was allowed to continue (dumb pilot or over water operation), the misfire can ruin the shielded spark plug lead, or even carbon track the magnetos distributor block, causing cross firing a different spark plug / cylinder at the wrong time.

Regarding Spyder spark plugs, they are not expensive. The 1330 uses a COP design, and as spark plugs age, the coils can become overloaded and internally fail. In extreme cases of failing spark plugs with a COP setup, a quality coil will not fail, but the discharge will burn thru the spark plug boot, finding the lazy path to ground, going around the spark plug, since that requires a huge effort with a failed spark plug resistor.

In simple terms, modern technology has given us spark plugs with exotic metals and electrodes that do not wear or erode away. In typical fashion though, the least expensive item in assembling a spark plug is the carbon resistor, and that least expensive item causes the issues.

Old school visually inspecting spark plug wear is no longer an option. Manufacturers test and know expected life of a spark plug before damage occurs to other more expensive items. Modern technology requires modern maintenance. Plugs are cheap.

Good information. We've had to replace a few coils. Almost always associated with a deteriorating spark plug. The Iridium plugs can look great on the outside. As PMK states, it's the internals that tend to fail. Some report going a lot further than the recommended 28k. And I would say 28k is probably low mileage on the current spark plugs. But the next scheduled interval is 56k. And that can tend to be a bridge too far. At least for 1 of the 3 plugs in a 1330. In my unscientific opinion, a lot depends on temperatures and RPM the plug runs at.

[BLUEKNIGHT911]

Good information. We've had to replace a few coils. Almost always associated with a deteriorating spark plug. The Iridium plugs can look great on the outside. As PMK states, it's the internals that tend to fail. Some report going a lot further than the recommended 28k. And I would say 28k is probably low mileage on the current spark plugs. But the next scheduled interval is 56k. And that can tend to be a bridge too far. At least for 1 of the 3 plugs in a 1330. In my unscientific opinion, a lot depends on temperatures and RPM the plug runs at.

I said this earlier in this thread..... MY 14 RT now has over 77,000 miles on the OEM plugs..... But I am going to try and change them this winter...... Mike

[Cobwebs]

I said this earlier in this thread..... MY 14 RT now has over 77,000 miles on the OEM plugs..... But I am going to try and change them this winter...... Mike

Would be interesting to check the resistance when you pull them out Mike. Also if you notice any difference with the new'uns.

[BajaRon]

I said this earlier in this thread..... MY 14 RT now has over 77,000 miles on the OEM plugs..... But I am going to try and change them this winter...... Mike

Do you intend to do the work yourself? We've developed some shortcuts which reduce the time and effort needed for this service. We intend to do a video, but just haven't yet.

[BLUEKNIGHT911]

Yes, I'm going to try ..... annnnnnnnnnnnnnnnnnnnnnnnd I will be sending in an order in to you soon .....Mike ...... also will do a resistance check on the old plugs ....Mike

[BajaRon]

Yes, I'm going to try ..... annnnnnnnnnnnnnnnnnnnnnnnd I will be sending in an order in to you soon .....Mike ...... also will do a resistance check on the old plugs ....Mike

If you agree to do a full report, I'll send you a set at no charge. I'm interested in what you find. Just PM me your address.

[IdahoMtnSpyder]

Just exactly what is the role of resistance in assessing the health of a spark plug? The only unwanted resistance I can fathom is between the electrode and the outer metal body of the plug. So is this a case of if that resistance drops low, i.e., approaching a short circuit condition, the coil has to put out more current than it maybe is designed for? We're looking at a parallel electrical circuit, the shorting path to ground and path through the plug gap so the total current is the sum of that which goes through each path.

I know from a test I did in college engineering lab when capacitive-discharge ignition modules were the fad back in the 60's, that the voltage applied to the electrode rises only to the point where current jumps the gap. If that happens at 10,000 volts, let's say, that is all the higher the voltage will rise to even if the coil is capable of putting out 50,000 volts. As I see it the only purpose of the built-in resistance in the plug electrode is to suppress the total milliamps (microamps?) of current that can flow through the plug when the spark jumps the gap.

Am I missing something?

[BajaRon]

Just exactly what is the role of resistance in assessing the health of a spark plug? The only unwanted resistance I can fathom is between the electrode and the outer metal body of the plug. So is this a case of if that resistance drops low, i.e., approaching a short circuit condition, the coil has to put out more current than it maybe is designed for? We're looking at a parallel electrical circuit, the shorting path to ground and path through the plug gap so the total current is the sum of that which goes through each path.

I know from a test I did in college engineering lab when capacitive-discharge ignition modules were the fad back in the 60's, that the voltage applied to the electrode rises only to the point where current jumps the gap. If that happens at 10,000 volts, let's say, that is all the higher the voltage will rise to even if the coil is capable of putting out 50,000 volts. As I see it the only purpose of the built-in resistance in the plug electrode is to suppress the total milliamps (microamps?) of current that can flow through the plug when the spark jumps the gap.

Am I missing something?

Resistance is designed to suppress EMI and RFI. Actually the 1st one covers pretty much everything. RFI is Radio Frequency Interference, which is a specific band of EMI (Electro Magnetic Interference). When the magnetic field collapses, it sends out radiation which can interfere with any kind of electronic signal, like radios, computers, etc. The correct amount of resistance suppresses this action. More resistance increases the load on the coils. Too much load heats them above operating temperature and can cause the coil to fail over time.

Most OEM wires use carbon impregnated fiber to carry the spark and provide resistance. This is an inexpensive way to produce wires but creates a very high resistance factor and it is subject to degradation with heat and vibration. As these wires degrade, resistance increases to the point where the spark may find an easier path and start arcing to metal components near the wire.

[Cobwebs]

If you agree to do a full report, I'll send you a set at no charge. I'm interested in what you find. Just PM me your address.

Carefull Mike, read the hair and makeup clause before signing.

[Knizar]

If you agree to do a full report, I'll send you a set at no charge. I'm interested in what you find. Just PM me your address.

WOW, Go Mike Go! You have about 3 months before riding season.

I'm very interested to hear how 70+K mile plugs check out after 9+ years in use.
Get Ur Done Mike.

Bill

[PMK]

Regarding coil failures. A fouled plug, will not destroy a coil. Simply, the energy travels to ground. A normal operation of a good plug, yes, the voltage required to fire the spark plug is determined by various factors. Compression ratio, BMEP, ignition timing, resistance of the plug, spark plug wire condition, resistance of the ground circuit, and more.

No doubt heat is bad for ignition coils, that heat will alter the resistance of primary and secondary segments of the coil itself.

Electronic ignitions, even battery ignitions or magnetos, do not like a high resistance or open high tension circuit. As resistance increases, the coils energy does best to be discharged. As resistance increases, the coil secondary windings can try to jump to the coils laminations. Other times, the windings will energize as the field collapses, and the path of least resistance will jump windings within the coil. Also, with these new COP setups, typically the plug resides in a deep cavity. There is a very short boot between to coil and plug. Since the boots position is between the resistor and coil, the misfire can deteriorate the rubber boot, burning it, and then misfiring to the metal ground of the cylinder head.

Regarding testing the plugs for resistance, typically the resistor is a carbon / graphite conductive material. Most commonly for powersports applications, that require resistor spark plugs, the value when new is 5-6 k ohms.

I have dealt with vintage motorcycle ignition issues, where 5k ohm spark plug caps had the carbon resistor ohm value increase to over 10k ohms. The higher resistance of the plug cap prevented the plug from firing at all. Swap the cap and starts in one kick.

We also deal with, and this is a serious problem, most of the spark plug manufacturers in the industry have stopped making non resistor plugs. Some owners, unaware there is a difference, have installed resistor plugs in ignitions not designed for them. Doing so results in various issues, most often, the ignition does not fire the plug, and in some cases, ruins ignition components.

[BLUEKNIGHT911]

WOW, Go Mike Go! You have about 3 months before riding season.

I'm very interested to hear how 70+K mile plugs check out after 9+ years in use.
Get Ur Done Mike.

Bill

Well about the mileage .....I made a mis-take ..... I actually have 80,626 ( it's been in my basement since Nov. awaiting a Full service including an HCM filter ) ..... So yes it's 70,000 + 10,626 = 80,626 mi....... Thanks for your offer Ron ..... I'll get in touch with you soon .....Mike