Piston check advice

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6/14/2018 8:39 PM

I have a 16 ktm 250f and was wondering what you all thought about how the piston looks. I'm not sure exactly how 4 stroke pistons should look and also if you look at the close up pic is that spark plug arc? It almost looks like the plug was arcing off it but I'm not sure so I'm hoping some experts can chime in, thanks. Photo
Photo

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6/15/2018 6:34 AM

What does it look like from the side?

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6/15/2018 2:12 PM

Photo
Exhaust side

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Intake side

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6/15/2018 3:58 PM

How many hours on the piston?

Paw Paw

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6/15/2018 4:01 PM

Paw Paw 271 wrote:

How many hours on the piston?

Paw Paw

20.7. Motorex oil every 3-5 hrs

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6/15/2018 7:18 PM

Overall the piston looks good. It shows to be a very little bit rich in fuel mix. Burn pattern looks very good.
I do see what I would call excess wear on the skirts of the piston for the run time stated.

Paw Paw

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6/15/2018 7:34 PM
Edited Date/Time: 6/15/2018 7:36 PM

Thank u paw paw. Any idea why there would excess wear on the skirts? Cyl was redone 20.7hrs ago and I'm a freak when it comes to air filters. I run either non ethanol or vp pro6. Also does it look like the plug is or has hit the piston or could be arching on it? The plug did not show any obvious sign

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6/15/2018 10:12 PM

ktm-5 wrote:

Thank u paw paw. Any idea why there would excess wear on the skirts? Cyl was redone 20.7hrs ago and I'm a freak when it comes ...more

Could have been detenation under heavy load?

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6/15/2018 10:15 PM

ktm-5 wrote:

Thank u paw paw. Any idea why there would excess wear on the skirts? Cyl was redone 20.7hrs ago and I'm a freak when it comes ...more

CarlinoJoeVideo wrote:

Could have been detenation under heavy load?

Oh yeah, I didn't even think about that, so that could've been from to low of an octane for a heavy load??

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6/15/2018 10:27 PM

I am concerned about the cylinder to piston clearance. If too much then it would allow the piston to wobble and cause excess wear. Also if under excess load at low rpms it will show excess wear on the piston skirt. Understand, you will always have some wear on the skirt, but this just looks excessive for the amount of hours posted or the hours of use were much more than reported.

Paw Paw

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6/15/2018 10:36 PM
Edited Date/Time: 6/15/2018 10:37 PM

That is one measurement I did not take because I had millennium redo the cylinder 20.7 hrs ago with the piston pictured and I just assumed there is no way it would be out of tolerance after 20hrs, unless they screwed up but I did send the piston with the cylinder. As for the amount of hrs I gave that is exact amount because I have always had hr meters on our bikes since the minis, and I'm not a guessing kind of guy, I want to know exactly, lol. I do know some piston wear will happen but wasn't sure if it was too much. If my son did not let the bike fully warm up at times would it look like this? I know 2 strokes will show the 4 corner sign if not warmed. Another side note also is the bike is modded fairly good so I don't know what kind of extra wear that would show if any. Thanks again

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6/16/2018 5:52 AM

What are the mods?

Paw Paw

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6/16/2018 12:06 PM

ktm-5 wrote:

That is one measurement I did not take because I had millennium redo the cylinder 20.7 hrs ago with the piston pictured and I ...more

Pistons tend to wear faster than cylinder

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6/16/2018 7:43 PM

Paw Paw 271 wrote:

I am concerned about the cylinder to piston clearance. If too much then it would allow the piston to wobble and cause excess ...more

Agreed. Check your clearence Clarence. I would bet it is set up a little too loose.

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