Conventional vs. Iridium spark plugs - Kawasaki Vulcan 750 Forum : Kawasaki VN750 Forums
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post #1 of 108 (permalink) Old 07-12-2012, 05:07 PM Thread Starter
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Conventional vs. Iridium spark plugs

everyone seems to be praising Iridium plugs in all the threads that i've read, and I use them on my '97. One day, just for the hell of it, i took one out of the left side, front cylinder, and turned the engine over while grounding the plug against the side of the engine, observing the brightness of the spark, then i replaced it with a conventional spark plug and the spark seems to be at least twice as bright. I repeated this test on the rear cylinder and got the same results. I've also noticed a slight stumble on hard acceleration and above 60mph. I have checked all vacuum lines for leaks, routed the carb vent hose to the right ear, being careful to cut it at a 45 degree angle, and I've also cleaned the main & pilot jets and checked the float bowl levels on both carbs and have seafoamed the fuel numerous times. Could my ignition coils be weak, do I need to sync the carbs? Also, plugs and wires are new. This is the second set of Iridium plugs that I've used, and the last set tested the exact same way. Really at a loss here, in spite of reading dozens of posts in this and other forums. Any ideas, anyone??

1997 VN750. 34K miles
(so far).
MCCT mod
Coastered
Lithium Battery
Iridium sparkplugs
Tuxedo stator mod
TPE stator rebuild
Engine guards
R/R relocated, upgraded to Shindengen MOSFET
LED turnsignals & brakelights
Electronic flasher relay
K&N air filters
OPT7 LED headlight bulb
Headlight relay mod
Pirelli MT66 front & rear tires
Plexifairing 3 Windshield
Digital LED voltmeter
(Aluminum luggage rack,
Floorboards,
Heel-Toe shifter .....all homemade)
synthetic oil
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post #2 of 108 (permalink) Old 07-12-2012, 05:13 PM
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Quote:
...then i replaced it with a conventional spark plug and the spark seems to be at least twice as bright.
Was it a Resistor Plug ?

'86 VN750 13,700 mi -Stock
-Purchased 2008 w/8800mi
Replaced ALL Cables . Kuryakyn LED Voltmeter
SilverStar Ultra 9003/HB2 H4 Headlamp, Jardine Fwd Controls,
Iridiums DPR7EIX-9 & Wires, Tuxedo Mod, Coil Mod, P/U Sensor Mod, Fork Seals,
Splines Lubed - 11/4/2012 - MF AGM Battery
Additional Flashing LED Brake Light on Trunk
Dampers went out @ 13+K !
After TOC MCCT's..... so amazingly quiet I discovered a rattling heat shield on my stock exhaust !
...have a vulcan good day!
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post #3 of 108 (permalink) Old 07-12-2012, 05:16 PM Thread Starter
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I'm not sure. I tried NGK iridium and then went to Denso

1997 VN750. 34K miles
(so far).
MCCT mod
Coastered
Lithium Battery
Iridium sparkplugs
Tuxedo stator mod
TPE stator rebuild
Engine guards
R/R relocated, upgraded to Shindengen MOSFET
LED turnsignals & brakelights
Electronic flasher relay
K&N air filters
OPT7 LED headlight bulb
Headlight relay mod
Pirelli MT66 front & rear tires
Plexifairing 3 Windshield
Digital LED voltmeter
(Aluminum luggage rack,
Floorboards,
Heel-Toe shifter .....all homemade)
synthetic oil
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post #4 of 108 (permalink) Old 07-12-2012, 05:42 PM
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I would look at the electrical connections to start....ALL of them!!
Start at the battery and inspect all connections, clean them and coat with dialectic grease to prevent oxidation.

You should have a good connection on the coils from the battery. the firing signal for the coils comes from the ignition, it will not produce a strong spark if the battery connections are dirty or if the battery is weak.

Also check your grounds and clean them as well...including the frame and battery box grounds.

this is just a starting point, but if you don't do this, you are just poking and hoping.
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post #5 of 108 (permalink) Old 07-12-2012, 07:06 PM
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I would check the potential at the primary coils.... are you getting ~13.5VDC?
If you have good voltage at the battery but it drops at the coils, try the coil mod and send full battery power directly to the coils, via a relay......
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post #6 of 108 (permalink) Old 07-12-2012, 08:38 PM
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As for the title. Conventional Vs. Iridium? I've had iridiums in my bike for about the last, oh, say 25,000 miles. I took them out recently & replaced them with some stock NGK plugs I had lying around till I get some new ones.

The material around the electrode on mine have fallen apart, swelled & look burnt (slight blister effect) I don't remember what the life expectancy was for them. Other than the crap around the electrode the plugs themselves look good.

So, did I notice a difference in performance switching back to a standard plug?
Not really.
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post #7 of 108 (permalink) Old 07-12-2012, 11:12 PM
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Quote:
Iridium IX®

The Spark Plug
Serious Enthusiasts Rely On

Designed specifically for the performance enthusiast. Iridium IX® offers extreme ignitability, improved throttle response and superior anti fouling

Fine Iridium tip ensures high durability and a consistently stable spark
Iridium alloy has extremely high melting point, perfect for today’s high-tech, high-performance engines
Trivalent Metal Plating - superior anti-corrosion and anti-seizing properties
Outstanding acceleration, high fuel efficiency and durability
Ultimate design, technology and performance.
Quote:
Standard Spark Plugs

The workhorse, at the heart of smooth-running engines around the world.

OEM Quality
Triple-Gasket Sealing Process
Consistent Performance
Plug of Choice in Millions of Vehicles
Quote:
FAQs - Spark Plugs

Q: When should I use a resistor spark plug?

A: NGK "R" or resistor spark plugs use a 5k ohm ceramic resistor in the spark plug to suppress ignition noise generated during sparking.

NGK strongly recommends using resistor spark plugs in any vehicle that uses on-board computer systems to monitor or control engine performance. This is because resistor spark plugs reduce electromagnetic interference with on-board electronics.

They are also recommended on any vehicle that has other on-board electronic systems such as engine-management computers, two-way radios, GPS systems, depth finders or whenever recommended by the manufacturer.

In fact, using a non-resistor plug in certain applications can actually cause the engine to suffer undesirable side effects such as an erratic idle, high-rpm misfire, engine run-on, power drop off at certain rpm levels and abnormal combustion.
All of these quotes are taken from the NGK website

when I worked for NAPA Auto Parts years ago, we always recommended NGK plugs for Motorcycles, weather it was for an old beater dirt bike, to the most high tech racing bike. They always outlasted and performed any other brand. We were real good about suggesting various brands and types of spark plugs to use in every thing from old Ford 8N Tractors to Fully built "Rice Tuners". I had a guy come in strictly buying Autolight plugs for his 1955 Willies CJ5. I told the guy to put some Champion plugs in his ride... I remember the old man was refusing to even try running Champions, because he said they were garbage. I told him to buy a set, run them for one oil change, and I would buy him 2 set of plugs and wires of his choice... if the plugs were fouled out or showed signs of accelerated wear. Well needless to say the gay came back three months later with 4 plugs in his hand, wanting to try some AC Delco, Bosch, NGK, and what ever else we could get our hands on... because he could not believe that the the Champions outlasted and out preformed the Autolights.

The moral of the story... The owners Manual recommends NGK for our bikes, just like Willies/Kiazer recommended Champions in the CJ5.

Last edited by slimvulcanrider; 07-12-2012 at 11:22 PM.
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post #8 of 108 (permalink) Old 07-13-2012, 12:20 AM Thread Starter
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After some investigating, and a cold beer or three, i've discovered that the previous owner, while installing an analog voltmeter, had crimped the (+) wire from the voltmeter into the same connector which plugs into the rear coil.....I assume so it would only have power with the key on. Wonder if this is the culprit? its getting late, so i will tackle it tomorrow. i guess it could go on the ignition relay instead....(its good to have a voltmeter after doing the stator mod). anyway, i hope this is the fix

1997 VN750. 34K miles
(so far).
MCCT mod
Coastered
Lithium Battery
Iridium sparkplugs
Tuxedo stator mod
TPE stator rebuild
Engine guards
R/R relocated, upgraded to Shindengen MOSFET
LED turnsignals & brakelights
Electronic flasher relay
K&N air filters
OPT7 LED headlight bulb
Headlight relay mod
Pirelli MT66 front & rear tires
Plexifairing 3 Windshield
Digital LED voltmeter
(Aluminum luggage rack,
Floorboards,
Heel-Toe shifter .....all homemade)
synthetic oil
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post #9 of 108 (permalink) Old 07-13-2012, 10:03 AM
Crap, I WAS in 5th gear.
 
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OK, I'm not exactly trolling, but fine wire iridium plugs (0.4mm) do not last as long as a conventional plug, and the spark is cooler (since the gap is smaller.) Autolite makes iridium plugs that have a 0.6mm electrode. I put these in my Expedition and there was a BIG difference. I put champion plugs in the VN750 (a.k.a. "lawn mower plugs") and it runs fine-- they were all I could get at the time. I will probably go with the Autolite Iridium XP if I can find them in the right size and heat range. The Bosch platinum plugs that have the ceramic insulator around the center electrode are total crap.
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post #10 of 108 (permalink) Old 07-13-2012, 04:46 PM Thread Starter
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The iridium plugs that are showing a weak spark are Denso IX22B....which are 5K ohm resistor plugs, according to the Denso website. My plug wire caps are also 5K ohm resistor....bringing the total resistance to 10K ohms. The plugs that showed a far bigger spark were NGK copper core DP8EA-9, non-resistor plugs. I can't find a non-resistor iridium plug that fits our bikes. Either I switch plug wire caps or spark plugs....

1997 VN750. 34K miles
(so far).
MCCT mod
Coastered
Lithium Battery
Iridium sparkplugs
Tuxedo stator mod
TPE stator rebuild
Engine guards
R/R relocated, upgraded to Shindengen MOSFET
LED turnsignals & brakelights
Electronic flasher relay
K&N air filters
OPT7 LED headlight bulb
Headlight relay mod
Pirelli MT66 front & rear tires
Plexifairing 3 Windshield
Digital LED voltmeter
(Aluminum luggage rack,
Floorboards,
Heel-Toe shifter .....all homemade)
synthetic oil

Last edited by Axelon20; 07-13-2012 at 04:49 PM. Reason: incorrect part number
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