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4 hours of damage... detonating?

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Ive been scanning through these forums for months now, this information is priceless! Well anyway just this past week I came across carvers timing page so I figured I may as well check mine. My bike is an 05 yz250, so i went for it. I quickly discovered that my timing was set at 1 degree advanced from stock. I proceeded to set it 1 degree retarded from stock to eliminate the possible detonation. Im running it on 94 octane pump gas (yes a station 1 mile from me sells 94).  Seeing the timing advanced made me a little nervous that it was detonating without me realizing it. So i continued to remove my jug just to find this... I just had the cylinder replated by millenium about 4 hours ago, along with a new oem top end. So good thing I caught it now. The marks on the cylinder walls are completely smooth and they dont seem to be affecting the plating at all. As for the piston, It looks like some detonating has been going on but I have had no experience to tell me for sure. Ive attached pictures. I guess my question is would the detonating change the dementions of the piston to the point where i would have to replace it? or could I just sand the carbon buildup off the top, throw in new rings and run it (being careful of any more detonation)

 

 

IMG_3708.jpg

IMG_6431.jpg

IMG_7143.jpg

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looks completely normal

Top of that piston looks a little different to me

Yz125

Kx250f

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This is just me, but since you have it apart, hone the cylinder and drop a new piston and rings in it. Then ride it like you stole it!

Edited by Rooster72

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Top of that piston looks a little different to me

Yz125

Kx250f

different how?

 

to the OP i would get a new set of rings and re-assemble. 1 degree off isn't going to do anything to your motor

Edited by Wild Alaskan

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Do not hone a plated cylinder.  Bead hone maybe.  I would just use a scotchbrite pad and some break cleaner. 

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Just clean it with some soap and water and a cylinder brush and re-ring it , it's fine.  I wouldn't use and abrasives on that nikasil . 

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I don't see any signs of detonation whatsoever. Are there burn marks across the edge of the rings? If not, I wouldn't bother replacing them if it were my engine, or hone the cylinder.

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That ting has only 4 hours? This is what the piston in my yz125 looked like after about 15-20 hours, along with a freshly plated cylinder

ImageUploadedByThumper Talk1400146274.618840.jpg

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Thanks everyone. I guess the thing I was worried about the most was the marks in the cylinder. I've never had it look like that on any of my bikes. Especially after 4 hours.

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Here's what my cylinder looks like, can't feel any the marks, can't really see them that will in this picture though

ImageUploadedByThumper Talk1400164039.809109.jpg

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Bazuka Joe, on 15 May 2014 - 03:31 AM, said:

That ting has only 4 hours? This is what the piston in my yz125 looked like after about 15-20 hours, along with a freshly plated cylinder

attachicon.gifImageUploadedByThumper Talk1400146274.618840.jpg

yours looks like that because your jetting is rich.the original posters piston shows his jetting to be much closer to perfect.

 

his piston also looks fine ,no detonation.i would reassemble as is .

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Looks fine. See those cylinder wall marks all the time on fresh replates until there are maybe 4-7 hours on it. 

Piston crown looks good, jetting is about spot on, good wash pattern. The carbon that is there is a bit thick, maybe due to whatever oil you are running. 

 

And yea, Bazuka Joe, yours is "clean" because it's jetted rich and the excess fuel keeps the carbon from forming. 

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Looks fine. See those cylinder wall marks all the time on fresh replates until there are maybe 4-7 hours on it. 

Piston crown looks good, jetting is about spot on, good wash pattern. The carbon that is there is a bit thick, maybe due to whatever oil you are running. 

 

And yea, Bazuka Joe, yours is "clean" because it's jetted rich and the excess fuel keeps the carbon from forming.

Yeah I've never replated a cylinder so I was a little paranoid. I'm running yamalube at 32:1. The jetting it's as close as I could get it with little adjustments with the pilot screw depending on weather, time of day etc.

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