Marks on new Piston??

rob27ma
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rob27ma
Edited Date/Time 7/24/2021 11:04am
Just put a new piston in my KTM 250, rode it for about 10 minutes, then pulled the exhaust to take a look. Upon inspection I noticed these strange wear marks on the piston. Should I be concerned?

The bike runs perfect, but it does seem to make more noise than the engine should. This was the reason I initially decided to change the top end.

The bikes a 2019 with 85hrs, and the position is a Vertex OEM replacement.

Any thoughts?

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willbilly
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willbilly 7/20/2021 5:05pm
7/20/2021 5:05pm
That’s strange. Did the piston have the black anti friction coating you see on four stroke piston skirts?
AJ565
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AJ565 7/20/2021 5:34pm
7/20/2021 5:34pm
That looks like the coating is straight flaking off. You said it has more noise then normal, what kinda gas are you running through it? Is it a knocking noise at higher RPM with a lite load on the engine by chance?
rob27ma
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rob27ma 7/21/2021 4:11am
7/21/2021 4:11am
willbilly wrote:
That’s strange. Did the piston have the black anti friction coating you see on four stroke piston skirts?
The whole piston was gray, which was different than the other Vertex pistons I've used before.
rob27ma
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rob27ma 7/21/2021 4:12am
7/21/2021 4:12am
AJ565 wrote:
That looks like the coating is straight flaking off. You said it has more noise then normal, what kinda gas are you running through it? Is...
That looks like the coating is straight flaking off. You said it has more noise then normal, what kinda gas are you running through it? Is it a knocking noise at higher RPM with a lite load on the engine by chance?
93 pump fuel, which I've always ran with this bike with no issue. The knocking noise seems to happen more on the lower idle than the higher side.

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mx724
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mx724 7/21/2021 8:12am
7/21/2021 8:12am
it could be that the cylinder is worn and there is some rocking happening with the piston in the cylinder?
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sandman768
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sandman768 7/21/2021 12:29pm
7/21/2021 12:29pm Edited Date/Time 7/21/2021 12:33pm
A or B piston? You want to use a B piston with the hrs you have on the cylinder. The coating is to aid the break in process, according to Vertex, eventually it would be worn off, but I would not be happy with the flaking either.
chump6784
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chump6784 7/21/2021 11:50pm
7/21/2021 11:50pm
I was talking to someone the other day who had ordered a Vertex piston for their sons KTM. The new piston that turned up was smaller than the one he took out even though they were supposed to be the same size. If its noisier at idel it sounds like piston to cylinder clearence is too big. I've also just had this issue with a Pro X piston too
Motorhead1812 7/22/2021 5:41pm
7/22/2021 5:41pm
Did the box that the piston came in show that it fit newer model 250s or did it stop at model year 2016? Despite the pistons having different skirt lengths, vertex did not update the part numbers, just the year fitments.

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