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Discussion Starter #1
Alright...I have a 16 yxz 3 pedal and it keeps misfiring on the center cylinder.. come to find out the coil gets cracked inside the cylinder head and leaves a white trace behind where it's arcing to the head... I bought new coils and installed them.. went for a 40 mile ride yesterday and wouldn't ya fricken know it... misfire,center cylinder, shit coil... HOW IS THIS HAPPENING???

P.s these are new coils from a yamaha dealer
 

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Maybe there is something keeping the spark plug from seating properly and you are getting cylinder gasses past the spark plug. Other than that, I would try a compression test. Maybe a cracked head? Any history here? Was there any work done recently, any overheating? Good luck.
 
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Discussion Starter #5
Maybe there is something keeping the spark plug from seating properly and you are getting cylinder gasses past the spark plug. Other than that, I would try a compression test. Maybe a cracked head? Any history here? Was there any work done recently, any overheating? Good luck.
No recent work done. I've had this problem a couple times last summer. Bought new coils, and wrapped them all with tape. Usually fixes the problem for a while.
 

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Interesting. Are they all getting brittle or just the center and all the other are still pliable and workable? Maybe you are running way lean. Any aftermarket exhaust or ECU tuning in place? Do you have a temp gauge installed?
 

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Discussion Starter #7
They are not brittle. One is new. All in great condition. Not running lean. Spark plugs look good. No aftermarket exhaust but we do have an Alpha stage 2 tune. Haven't installed the temp guage yet.
 

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Don't forget the plug can also leak where the ceramic and base join and sometimes cause it to leak where the tip and ceramic meet.
 

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So if the coil has the carbon tracking on it then you have to replace the plug and coil at the same time because the carbon will be on both the plug and coil if you only change one then it can rune the other part you didn't change and put some sort of dielectric grease on it to help prevent moisture
 

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Assuming no mechanical issue in that area, put some dielectric grease on them before install. Any contamination by greasy hands or sweat can cause arcing across the insulator and eventual failure.
 
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