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Discussion Starter · #1 ·
I was checking my plugs after running a short distance across a lake yesterday and both of them looked pretty close. The question I have is why does 1/2 of my insulator look white / light brown and the other side of it black? I know it has something to do with what angle the fuel is flowing by it but what side do you go by? Am I rich or Lean? I believe they make a spark plug shim kit to stop this but I'm not convinced I need to go that far. Does anyone have any helpful knowledge on this subject?

I believe it's caled Spark Plug Indexing. Do you set the plug so the open end if facing the carborator / reeds or do you face it towards the exhaust valves?
 

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"The intake side does not make the best HP with rear pointed plug gap. Always when we get HP improvement it is gap pointed toward exhaust, which really is where the final intake charge gets pumped back into the cylinder before ex port closes.

If you optimize plug orientation, you can hope for maybe 1% improvement over worst orientation. If you roll the dice when you install plugs, you won't gain or lose much. But for stock class draggers who need every tenth of a HP it is worthwhile. But please dont point them toward te back of the engine."


This is a direct quote from D.T. Jim as posted on Snowest. Hopefully he doesn't mind me copying it. So, towards the carbs would be the worst.


As for reading plugs, this will tell you all you need to know. http://www.kawtriple.com/mraxl/plugread.htm
Get a plug reading light, or an otoscope from Ebay. Plug color on the tip means nothing, its just deposits from the particular gas, or oil your using. The smoke ring at the base of the plug is what tells you the air/fuel ratio.

For some reason I can't put in the exact name of person in quotes. He runs the no. 1 dyno facility in the country though.
 

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Discussion Starter · #4 ·
Thanks for the replys. I think I'm still unsure which direction the gap faces? Also, maybe I don't even need to Index my plugs. Does your plugs look like mine? Half and half. If so what side do you read?
 

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your running a trail sled so why worry about indexing your spark plugs ? jet it down 1 or 2 sizes smaller to start with and use the link to help you figure out where your at. I am guessing you didnt hae enough run time on the plugs to change the color compleatly.

http://www.dansmc.com/Spark_Plugs/Spark_Plugs_catalog.html


If you have new plugs they take time to color up , its easier to read older plugs with some miles on them. I am still running the same plugs for the last 3 years , if you dont over use the choke and never foul a plug theres no reason to change them. Its very possible that the oem spark plugs could out last the the service life of the motor. Once your close to dialed in on the fuel and oil the plugs really dont get deposits on them.
 

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Discussion Starter · #6 ·
your running a trail sled so why worry about indexing your spark plugs ? jet it down 1 or 2 sizes smaller to start with and use the link to help you figure out where your at. I am guessing you didnt hae enough run time on the plugs to change the color compleatly.

http://www.dansmc.com/Spark_Plugs/Spark_Plugs_catalog.html
If you have new plugs they take time to color up , its easier to read older plugs with some miles on them. I am still running the same plugs for the last 3 years , if you dont over use the choke and never foul a plug theres no reason to change them. Its very possible that the oem spark plugs could out last the the service life of the motor. Once your close to dialed in on the fuel and oil the plugs really dont get deposits on them.[/b]
Thanks XC-Mark

I have about 60 miles on the plugs. I'm not sure how long you need to run the motor before they color?
 
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