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burnt oil on piston?

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this is the second top end ive done on my bike and i noticed this time that there is a lot of black on the connecting rod and under the piston, is this because im using to much premix? 36:1 100_81021.jpg

the piston on the left is stock, on the right is Pro-x. my bike is a tad rich but i dont think it should be that black under the piston.

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It looks to me like its running a little dirty, what ratio do you mix your gas/oil at? Are you running a good synthetic oil? Whats the rest of the pistion look like? Lots of blow by?

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my bike ran hot the other day it was between 204 and 215 on the temp sticker but i was riding it in sand and going no faster than 2nd, my bike normally runs at 175 or cooler. im using yamalube 2-r with 110 race gas at 36:1. the only thing ive done is put vforce and jd jetting in. yes its a little rich but not by much. even on my top reed petal there is burnt oil. on the blow by there is a little more than the stock piston had on it but not that much.

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I agree with Chokey that it looks like it's been run very hot. So hot that the oil/fuel mix entering the crank area is sticking to the bottom of the piston, burning incompletely, then carbonizing....which can't be good for any bearing in there.

Sounds to me like your oil/fuel ratio is too lean on oil, not too rich. If it was richened up a bit, your engine would be running cooler and not heating up that piston so much. I'm surprised it hasn't seized....or has it?

Karl

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