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NGK Iridium Spark Plug Gapping

11K views 5 replies 3 participants last post by  techyiam 
#1 ·
After installing an 8" mini delkevic exhaust at ~6,500 miles my bike seemed to pop quite a bit after letting off the throttle, as expected. Recently it has been doing so more often and I noticed a lack of power in lower rpms.

Before changing the air filter I wanted to inspect/ change the spark plugs which I thought might give me an indication of whether the AFR is running lean or rich.

at 7,500, just last week, I replaced the stock plugs for the NGKCR8EIX plugs and through the consult of an autozone 'expert' I gapped the plug both at ~.030-.035 in. The IX spark plugs were originally set at 0.025 in. and I realized after installing them that iridium plugs are factory gapped to model specifications. :wacko:

Personally I feel as though increasing the gap size would provide more probability for electron collision, therefore greater fuel combustion. But in the same token if the bike does not compensate by increasing its voltage output then increasing the gap would have the opposite effect? Thus far, the bike has been running much better than before the spark plugs were replaced, in essence it is a lot more responsive, but its only been a week.

Im not knowledgable in the topic so if gapping the iridium spark plugs I used was a horrendous mistake, please let me know ! :emot-pray:



as far as the old plugs go, I have attached a couple of pictures for some additional advice. I am sorry if i sound ignorant but they seem to be a combination of tan, black and white so I am not quite sure whether my bike is running lean, rich, or perfect haha any clues? :grin2:
 

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#2 · (Edited)
Reading the plugs, your bike is not running rich. If it were running rich, the firing end of the spark plug would be blackened, something fairly easy to spot. However, your engine could be running a little lean (I am assuming that the image and my monitor color calibration are not too off). The "white" insulator is a little more white than normal (especially with only 0.025" gap and stock ignition system). However, it is possible for an engine to have white looking insulators and be running correctly. The plugs in my engines are white, rather than "tan" colored, but are running fine. But I use a more powerful ignition system, and I didn't switch to colder plugs. Note that the heat range of a plug is another factor that can affect the color. But if your plugs are stock, implying the correct heat range is used, then the insulators could have been a little more "tan" colored.

I would not consider the old plugs worn. The edges of the center electrode do not look that rounded. The firing end of the old spark plugs look pretty clean (not fouled, have deposits, etc). If you were to reuse them, I would clean up the threads a bit, though (better for the spark plug threads, and better performance). And probably bring the gap back to stock spec's.

The NGK Laser Iridiums "IX" are single-sided spark plugs. It has an iridium tipped center electrode, but the ground electrode is just conventionally nickel plated. They won't perform as well as double-sided ones. However, IX's can still offer better performance than the stock ones. Noticed how much more slender the iridium tip over the stock plug's center electrode. The iridium center electrode can provide much longer life, and would require lower initialization voltage, and potentially more performance.

According to the Ninja 300 Service Manual 2nd Edition, the stock spark plug gap should be between: 0.028" to 0.031".

If the old plugs were gapped to 0.025", then you could have experienced slightly less performance (less sharp throttle response, or power perhaps), but then the spark plugs would last longer.

With your new IX's in there, my feeling is that they can be gapped a little bigger than stock, so having a gap of 0.035" should be fine (this should give a little more performance). The IX's center electrode's fine tip would lower the required initialization voltage over stock. Plug life should still be much longer than stock because the center electrode has an iridium tip.

It is possible to lose some throttle response over time since the plug would have lost the really sharp edges (higher initialization voltage would then be required), but with a fine tip, the performance should still be good.
 
#3 ·
Great response, thank you! I didn't think the 0.035" gap on the IX would be too detrimental either. In fact, the bikes overall performance seems to be better than when I bought it. That being said I bought it with 4,500 miles and, I now know based on working on the bike myself, the previous owner did not keep up the bike very well.

Let me know if there are any tall tale signs caused by improperly gapped plugs. I would imagine it would be along the lines of lack of power, misfiring, knocking, lack of response, etc.
 
#6 · (Edited)
...

Let me know if there are any tall tale signs caused by improperly gapped plugs. I would imagine it would be along the lines of lack of power, misfiring, knocking, lack of response, etc.
Here's what NGK says:

"WHAT IS THE MAXIMUM I CAN OPEN OR CLOSE THE GAP?
A: We do not recommend adjusting the spark plug gap < or > .008". The reason for this is the ground electrode and center electrode won't line up properly, hindering spark plug performance too."

"Dark coloring, such as heavy black wet or dry deposits, can indicate an overly rich condition, too cold a heat range spark plug, a possible vacuum leak, low compression, overly retarded timing or too large a plug gap."

There is certainly a learning curve when one wants to use big gaps. But for 0.004" over spec, and replacing nickel-plated with iridium tip plugs, it is unlikely you will experience negative effects. ( I am assuming that your IX's are now gapped at 0.035". )

If it runs well now, you should be golden, IMHO. Degradation of performance over time for iridium tip plugs are usually better than for conventional nickel-plated ones too.
 
#4 ·
@as13ad, your original NGK plugs were burning fine, i.e., not lean not rich. and showing only slight wear. The plug on the right in your photos is revealing a slightly leaner mixture than the one on the left though. Here's a comparison chart to help you:



Luckily, even with your shorty exhaust, your plugs closely match the optimal example on the right. If your original NGKs weren't misfiring there was absolutely no reason at all to replace them at only 7500 miles as spark plugs are designed to last much much longer than that. The only maintenance is to gap them periodically as the gap will tend to open up over time. The proper spark plug gap is .028 - .031" per the owner's manual and that's exactly what you should use.

asiad said:
Personally I feel as though increasing the gap size would provide more probability for electron collision, therefore greater fuel combustion.
LOL, DUDE... personally I feel you've been smokin' some of Colorado's finest making a comment like this. Again, stick with Kawasaki's recommended values and of course lay off the 'herb' while you're riding.

Cheers from Thailand! :grin2:
 
#5 · (Edited)
From the horse's mouth: NGK

"In general, a light tan/gray color tells you that the spark plug is operating at optimum temperature and that the engine is in good condition."


"Normal Condition
An engine's condition can be judged by the appearance of the spark plug's firing end. If the firing end of a spark plug is brown or light gray, the condition can be judged to be good and the spark plug is functioning optimally. "


"Dark coloring, such as heavy black wet or dry deposits, can indicate an overly rich condition, too cold a heat range spark plug, a possible vacuum leak, low compression, overly retarded timing or too large a plug gap."

Source:

http://www.ngksparkplugs.com/about-ngk/faqs/spark-plug-faqs/how-do-i-read-a-spark-plug
 
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