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Discussion Starter #1
We have an Indy 500 that has a shaved head on it. When a friend finished rebuiliding it, it wouldn't run right for him with the stock plugs in it. He replaced the RN3C's with BR9ES. It ran okay for a few hours that way, then it began to foul out plugs every couple minutes at all rpm's within the powerband. The plugs on both cylinders seemed very black. We just changed the plugs back to the stock plugs (RN3C) and now it really runs good and the insulator is a light brown as can be seen below. Do you think this color looks good, or too hot. I don't have much experience with measuring the color of spark plugs. Thanks.[attachment=50705]
 

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Looks great. Did you do a plug chop or is that just from running.
 

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Color looks good to me, how long did u run with that plug in?
 

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Discussion Starter #5
Sorry, I don't know what a plug chop is. . . Is that when you just run it at one throttle setting and then kill it? We ran it around the field through varying throttle settings about 4 miles or so. We did a preliminary measurement after riding less than 1/16 of a mile first just to make sure they weren't white, and when they looked brown, we did the longer run.
 

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You need to run it wide open and then hit the kill switch while holding throttle open. Don't let it idle. Then check color.
 

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Looks perfect to me but... At what temp did you make the test, and of course a plug chop is the proper way to check it correctly[;)]
 

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PLUG CHOP??? Explain.
 
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