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Old July 25th, 2019, 01:55 AM   #1
nocturncal
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Reading Spark Plug

Just pulled my spark plugs to replace them with iridium plugs (I didn't change em with the valve adjustment due to wanting to learn one thing at a time). These plugs have been on for 17,000 mi and the gap when I pulled em was ~9mm (ruh roh).

From reading in the internet, they look like my bike running rich? Am I missing anything else?



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Old July 25th, 2019, 07:01 AM   #2
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What you are looking at is an overall average of everything - from idle mixture to WOT mixture over a significant time period.

Isolating one specific area for change based on those average readings is not possible.

Is it all stock? How does it run? Any hesitation? Have you made adjustments to the idle mixture screws which are usually set too lean from the factory? Shimmed the needles to richen the midrange? Typically the stock Main Jet is overly rich, especially with a stock intake and exhaust.

An exhaust gas analyzer on a dyno would tell you exactly what's going on, but for most some simple moderate tuning will do the job.
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Old July 25th, 2019, 08:34 AM   #3
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for those owners without dyno....longer term fuel consumption (MPG) also a helpful, determining factor in revealing overall engine efficiency, carb setup, etc.
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Old July 25th, 2019, 01:30 PM   #4
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I thought I heard that iridium plugs can often used a larger gap than standard copper plugs. I may be wrong about that but thought it was possible due to the smaller, more focused electrodes being better at firing a spark from the same coils.

I thought briefly about putting platinum or iridium plugs in my bike for better performance or fuel efficiency, but thought the cost difference would not be offset by any fuel efficiency gains. More than that, I like to read the plugs and don't want to pay for new costly plugs or reuse the integrated crush washers each time. When our Ninja came out in the 80's car manufacturers were just starting to use platinum plugs. Now just about all new gas cars call for iridium plugs. I'm curious but don't know about new bikes.

I'm also unclear how much the newer spark plugs improve car engine performance, efficiency, or emissions. I think the manufacturers are more concerned about car owners not changing the spark plugs and blaming the car for a resulting loss in performance when it starts missing or stops firing on all cylinders. With the new iridium plugs most cars won't need them replaced until around 100,000 miles, safely past all vehicle warranties. If I had to pay a garage to change the plugs or if it was hard for me, I'd use newer plugs.
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Old July 25th, 2019, 01:56 PM   #5
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Main benefits of platinum and iridium plugs is durability giving you longer intervals between replacements. No performance benefits whatsoever. Sure, replacing old worn-out plugs with new will restore degraded performance back to stock. And this is what has been noticed by many as "improved performance". However, dyno-tests has proven over and over again that iridium plugs cannot give better-than-stock performance.

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Old July 25th, 2019, 02:24 PM   #6
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My understanding is with a Platinum or Iridium plug the gap doesn't increase like a traditional plug so the change interval can be much longer.

Not much of an issue with a cycle engine for the most part, but for some auto engines it's a major project and/or very expensive to change them so the extended service life would be a big advantage.
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Old July 25th, 2019, 03:05 PM   #7
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yeah, on some cars, you almost have to remove engine to change plugs!
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Old July 26th, 2019, 08:43 AM   #8
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Quote:
Originally Posted by jkv45 View Post
What you are looking at is an overall average of everything - from idle mixture to WOT mixture over a significant time period.

Isolating one specific area for change based on those average readings is not possible.

Is it all stock? How does it run? Any hesitation? Have you made adjustments to the idle mixture screws which are usually set too lean from the factory? Shimmed the needles to richen the midrange? Typically the stock Main Jet is overly rich, especially with a stock intake and exhaust.

An exhaust gas analyzer on a dyno would tell you exactly what's going on, but for most some simple moderate tuning will do the job.
The carb is all stock, no adjustments made. The engine fully up at idle has some hesitation (the idle will drop to 900rpm, then pick up to 1200rpm. Idle seems to be a bit better after I changed the spark plugs but could be placebo effect tho.

I mostly wanted to change the spark plugs to iridium because I wanted plugs that would last a long time and wouldn't need to be regapped as frequently

As far as MPG goes, l get roughly 215 miles to the tank
-- all city driving with the steep hills of San Francisco.
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Old July 26th, 2019, 08:48 AM   #9
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Quote:
Originally Posted by Theorist View Post
I thought I heard that iridium plugs can often used a larger gap than standard copper plugs.
Does the gap need to be slightly bigger for iridium plugs? I measured the gap between 0.7 < x < 0.8 using the motion pro tool. The gap out of the box didn't seem to be wildly off of spec
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Old July 26th, 2019, 10:27 AM   #10
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Quote:
Originally Posted by nocturncal View Post
The carb is all stock, no adjustments made. The engine fully up at idle has some hesitation (the idle will drop to 900rpm, then pick up to 1200rpm. Idle seems to be a bit better after I changed the spark plugs but could be placebo effect tho.

I mostly wanted to change the spark plugs to iridium because I wanted plugs that would last a long time and wouldn't need to be regapped as frequently

As far as MPG goes, l get roughly 215 miles to the tank
-- all city driving with the steep hills of San Francisco.
You could benefit from some carb tuning.

Most of what you want to do requires carb removal, which can be challenging especially the first time.

Basically you want to remove the caps from the idle mixture screws and set the screws to 2.5 turns out. Most likely they will be around 1.5 out stock.

Shimming the needles will richen the midrange and reduce a hesitation in that area if it has one.

The Main Jet is a bit rich, and you can search around here for a recommendation to optimize it.

When properly tuned you will get smoother throttle response as well as better mileage.

You may also have a vacuum leak, so check the carb clamps to make sure they are snug. You can also spray some carb cleaner on the junctions from the carb to the engine and listen for a change in RPMs if you have a leak.

Syncing the carbs in the final step.

This section has more carb and tuning info that may help - https://faq.ninja250.org/wiki/Intake
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Old August 1st, 2019, 09:23 PM   #11
nocturncal
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Thanks for all the replies!

Replacing the spark plugs solve my fluctuating idle. Once the engine is warmed up, my engine will idle at 1200rpm and not wildly fluctuate.

I do plan on taking the carbs apart and tinkering with them in the coming weeks. I wanted to tackle different parts of the bike one at a time to make it simple for me to learn.
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Old August 1st, 2019, 09:33 PM   #12
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Quote:
Originally Posted by jkv45 View Post

Syncing the carbs in the final step.

This section has more carb and tuning info that may help - https://faq.ninja250.org/wiki/Intake
I've sync'ed the carbs a couple of months ago using the two bottle method on the Ninja wiki. Totally understand now that this is the last step and cleaning the carbs should have been done first.

At the time I had just done the valve adjustment (first one ever!) and wasnt confident about tinkering with another system of the bike. I was afraid that I'd mess something up and be stuck with trying to diagnose whether it was a valve adjustment problem, carb problem, or a combination of both as a result of me messing around with different parts.
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