SX 250 Piston wear

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10/24/2020 7:59 AM

Hello guys
I just got a "new" SX 250 2019.
56 hours in it.
The old owner told me he did the piston at 44 hours.

Here is the piston:
Does it look like a 12 hours piston or is this the original one?
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rarararaataatatatata

10/24/2020 8:04 AM

Look at the nuts that hold the cylinder to the crankcase. Do they have fresh tool marks?
Your piston looks ok to me.

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10/24/2020 8:38 AM

JWACK wrote:

Look at the nuts that hold the cylinder to the crankcase. Do they have fresh tool marks?
Your piston looks ok to me.

Yeah. It looks like it has been opened.
What do you think? Photo
Photo

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rarararaataatatatata

10/24/2020 8:41 AM

JWACK wrote:

Look at the nuts that hold the cylinder to the crankcase. Do they have fresh tool marks?
Your piston looks ok to me.

MZ193 wrote:

Yeah. It looks like it has been opened.
What do you think? Photo
Photo

I would say it has.

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10/24/2020 8:44 AM

That baby looks fresh

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10/24/2020 8:47 AM
Edited Date/Time: 10/24/2020 8:55 AM

The old owner speaks the truth. You have nothing to worry about.

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Non Gratum Anus Rodentum

10/24/2020 8:58 AM

I think they recommend replacing every 20 hours?

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10/24/2020 9:12 AM

friday10 wrote:

I think they recommend replacing every 20 hours?

Yeah, and oil every 30 minutes.
All of my friends on sx/tc 250 are doing 40/60 hours on top end, 100/140 hours on crank/bearings.

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rarararaataatatatata

10/24/2020 9:48 AM

That is a fresh top end for sure. No blow by past the rings and nice horizontal machining marks on the skirt. I've done top ends on those bikes way past 60 hrs. and they still looked good. Air filter maintenance is the key.

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10/24/2020 10:21 AM

friday10 wrote:

I think they recommend replacing every 20 hours?

MZ193 wrote:

Yeah, and oil every 30 minutes.
All of my friends on sx/tc 250 are doing 40/60 hours on top end, 100/140 hours on ...more

I've got 80 some hours on my 300, and it still runs perfect. Compression is the same since new. Put a piston in my friends 300 at 88 hours and it spec'd perfect, ring end gap was well within spec. My other bro pushed his to 150 hours before a piston change....that's a bit long for my taste, but it lasted.

Riding style varies between all of us as well.

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Tomac and/or Anderson for 2020.....

10/24/2020 10:38 AM

You can see the chamfer on the rings and looks good to me!

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Don’t piss off the old people - the older they get the less “life in prison” is a deterrent for them!

2020.5 KTM 450 SXF FE
2006 KX250

10/24/2020 5:19 PM

So I’m gonna point out that the nuts and bolts look like they’ve been tightened down. I don’t see witness marks that they’ve been loosened.

Also in terms of wear this is my piston with 90 hours on it and it has about the same wear. Photo
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2018 KTM 250sx
Instagram CamaroAJ

10/24/2020 5:25 PM
Edited Date/Time: 10/24/2020 5:26 PM

You know that every seller that says fresh top end is a liar don't you? I learned that here on Vital.

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The older I get, the faster I was.

10/24/2020 7:09 PM

Really you should look at the old piston. That will tell the story if anything is going on

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10/24/2020 7:22 PM
Edited Date/Time: 10/24/2020 7:23 PM

Blade Flanagan jr. wrote:

That is a fresh top end for sure. No blow by past the rings and nice horizontal machining marks on the skirt. I've done top ...more

I bought a pretty low hour 2003 kx250 that had been ridden but clearly still somewhat low in the hours. I've owned it for a year and a 1/2 and towards the end of last season the compression was getting low so I knew it knew the piston had to be replaced.

Low and behold my surprise when I cracked that engine open for the very 1st time it still had the original piston in it after 17 years including the rings ! The engine had never been opened until I put a new top end in it about 2 months ago.

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10/25/2020 1:46 AM

Just throw a new piston in it then you know for sure, 2stroke pistons are cheap enough and easy enough to swap out. Why risk it? I always throw a new piston in if i buy a second hand bike no matter what the hours. Its easy to disconnect the hour meter once it gets to a certain point so you can never trust a second hand bike.

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10/25/2020 2:38 AM

What piston do you recommend for my bike?

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rarararaataatatatata

10/25/2020 5:43 AM

Vertex

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10/25/2020 5:43 AM

If you’re concerned about it just put a new one in. It is super cheap to do and gives you the peace of mind you’re looking for. Otherwise it may end up like mine this summerermm Photo
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