Strange spark plug failure?!

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Lookin' Around
Lookin' Around
Posts: 13
Joined: Mon Apr 30, 2018 2:18 pm

Hello everyone! I have the bike for two months, now.
About two weeks ago I rode the bike for about 35 km, the next morning I crank the starter, she fires up but runs extremely rough and has no power. After examination I found out that the original NGK CR8E spark plugs on cylinders 3 & 4 have failed and she ran on only 2 cylinders. After I changed the spark plugs with new Denso u24esr-n ( plug gap 0.7) she ran well for about 100 kilometers. Then the same thing happend, I rode the bike ( runs like a champ), I turn it off and the next morning when I fire her up she runs only on 2 cylinders, this time the new spark plugs on cylinders 1 & 2 have failed. I put on a new set of 4 plugs and this time after only 10 km on the next morning the spark plugs on cylinder 3 & 4 have again failed.
When she works fine with the new plugs the color of plugs 1 & 2 is light brown tan, plugs 3 & 4 are black. I tryed leaning out the air fuel mixture by tightening the screws but with no luck. Carbs are synched btw. Its a mistery to me why she runs fine the evening before, and on the next morning the plugs are gone, like it happens overnight while she is just sitting in tha garage. They havent failed on me while riding. This will be my 4th set of plugs and it's getting damn expensive. I though this can be a problem with the coils but coil 1 is for plugs 1 and 4 and coil 2 for 2 & 3, but my plugs fail in pairs 1 & 2 and 3 & 4. My mixture is rich on cylinders 3 & 4 as I mentioned earlier, ( I know that spark plugs can fail because of a lean mixture). When the engine is cold it start withouth the need of a choke ( again indicating the rich mixture), if I pull the chocke she starts to run rought and bogs down. Another thing I want to mentione is that I do tend to ride aggressively, but she burn 8L/100km of fuel ( 28 - 29 mpgs). This is my first multicylinder bike, but I think that's A LOT.
This is my other post, there I have writen what I have done to the bike upuntil now so you can get a better idea of the picture.
Any help and suggestions are welcomed! :)

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