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Discussion Starter · #1 ·
Rightly or wrongly I have ordered some more Irridiums to replace my last set which were one step colder than stock. I have the OE 108 kit with 10.25 pistons and understand that this combination needs perhaps even two steps colder rather than the one step I've been using.


My question is what would tell me that I have gone too cold and should go back to the one step colder. My bike really pings sometimes especially on hot days in the Rockies with the one step colder plugs so I'm hoping I may help this a little with the even colder plugs. Thanks:}
 

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fcwarrior said:
Rightly or wrongly I have ordered some more Irridiums to replace my last set which were one step colder than stock. I have the OE 108 kit with 10.25 pistons and understand that this combination needs perhaps even two steps colder rather than the one step I've been using.


My question is what would tell me that I have gone too cold and should go back to the one step colder. My bike really pings sometimes especially on hot days in the Rockies with the one step colder plugs so I'm hoping I may help this a little with the even colder plugs. Thanks:}
from my hot rodding days IIRC if the plugs are too cold, it will not burn/combust efficiently. Thus your plugs will not burn off all the fuel and carbon deposits on the tip. Your plugs will essentially look similar in the case where you are running too rich...

FWIW, I like the iridium plugs and feel an improvement. Of course I have no scientific data to prove it. But I did go from regular oem plugs to the iridiums that were one step colder. It felt more responsive and I got less pinging as well... Let me know if going two steps colder worked for you. I may just try that next go around....
 

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This is a lot of info however it will provide you with specific know-how. There are different techniques and methods, wade thru these and you'll have eyes open to a world of info at your spark plug tips:


Spark Plug Condition Chart: http://hawkworks.net/sparkplug-chart/
Spark Plug Condition Chart: http://www.ngksparkplugs.com/techinfo/spark_plugs/faq/faqread2.asp
Spark Plug Condition Info: http://www.strappe.com/plugs.html
Spark Plug Reading - Racing: http://www.usaimports.co.uk/Mopar_Tech_Pages/Spark_Plug_Reading.htm
 

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Discussion Starter · #5 ·
Great info thanks!!


I did a search on the 4M and got a 9EIX as stock. My plugs are 8EIX so I ordered 7EIX to go colder still.


Now, on the NGK website, they state 7EIX is standard so effectively I've gone back to stock. Sheesh, Now I need to order the 9EIX for two colder:}
 

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IMO the problem with this plug chart is its too generic and doesn't provide detail as to why. Also, the pics show several ashen examples that are too close to eac other, again without enough detail as to why. Some of the guys who suggested the 4 posted above had it right I think. Its a lot of info, but its everything you need to know (including which brands use larger part#'s for a hotter plug versus which use higher part#'s for a colder plug). The first 3 that I posted above are great info with reasonably clear pics, but the arealso excellent'primers' for understanding the 4th link, which has been a well-kept secret for years.


mdfdwarrior said:
Here are all the picture comparisons on one page....http://www.dansmc.com/Spark_Plugs/Sp...s_catalog.html
 

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Here's data from thePopular Mods post in the Technical forum:


Spark Plugs - OEM: NGK DPR7EA-9 - or - Denso X22EPR-U9 from factory (gap 0.8mm to 0.9mm)
Spark Plugs - Preferred: 4 each NGK Iridium DPR7EIX-9 (7803) 0.032" ~ 0.035" (0.8mm to 0.9mm)


I know you are working with an engine CID increase. Depending on the brand, as you now realize, don't assume a higher plug part# is hotter!
But also don't assume arbitrarily that HEAT RANGE is your fix. There's other engine factors to consider first, not the least of which is timing. That is the purpose of the four links (above) about learning to read yourspark plugs like a racer who also works on his family car.


Just to confirm that the ground work has already been done, the stock part# above comes from the 2003 owner's and 2002 service manuals. The NGK website at http://www.ngksparkplugs.com/part_finder/motorcycles/step4.asp?id=2682&type=regagrees with the part# above (plus agrees with the Iridium part# above). All model years use the same OEM plugs.


Here's the NGK spark plug part# key, notice higher part numbers are colder:


http://www.ngksparkplugs.com/docs/tech/partnumberkey.pdf








fcwarrior said:
Great info thanks!!


I did a search on the 4M and got a 9EIX as stock. My plugs are 8EIX so I ordered 7EIX to go colder still.


Now, on the NGK website, they state 7EIX is standard so effectively I've gone back to stock. Sheesh, Now I need to order the 9EIX for two colder:}
 

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Spark Plug Reading - Racing: http://www.usaimports.co.uk/Mopar_Tech_Pages/Spark_Plug_Reading.htm

You are talking about heat range. Look at the threads on the plug for this. If you get it too cold the engine will misfire and your fuel consumption will increase. The ceramic and ground strap will be on the sooty side also.There is more ceramic insulation on a colder plug to retain the heat better- Less insulation on the hotter plug so that the heat travels faster into the head.


Most of the examples in the pictures are extreeme and are of little use in most cases.
 

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First, i hope you are running super unleaded...next, I wouldn't think that the tempurature range of the plug would have that much effect on detonation, but, those links have a lot of info to sort through.


Second, if you are controlling advance, you need to retard it some...detonation is a real motor killer and our PCM's don't do anything to retard the ignition if it starts to knock.


Last, consider your intake...if you can cool the intake air, you can run more timing, what kind of intake do you have (I expect it is not stock)?
 
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