2002 CR125/134 'localized pitting' in cylinder...normal?

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2/13/2019 7:02 AM

Just bought 2002 CR125 that was bored to 134 and then replated.

Developed a leak at a head bolt, so popped the head off to swap the gasket. I potentially have a warped head, and I know the deck at the exhaust end of the cylinder is weak anyway...so I'm still looking at that.

What I'm wondering is...is it normal to have a very localized pitting area in the cylinder? Yes, drag a fingernail and it's enough to grab...but only in this one area (about 9 o'clock if looking from intake).

If the cylinder was bored/replated/bored, then had about 7 hours of riding since the work was done, how does localized pitting show up?

Any answers will be appreciated. Photo
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2/13/2019 7:40 AM
Edited Date/Time: 2/13/2019 7:47 AM

I would be concerned if they showed up after the plating process, means the Nikasil is coming off. If they were visible during the plating process then I would say they are acceptable porosity pits. See the Millennium video, they deal with it daily.

https://www.millennium-tech.net/vidplayer.php?id=34

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2018 KX450F
2005 KX250
2003 KDX 220
1984 KX 80
1982 RM 80
1980 RM 80
1977 XR 75
1969 Honda Mini 50

2/13/2019 7:50 AM

Thanks. I researched the porosity pitting last night, and I agree with you.
Just seemed weird that it is so localized.
I didn't own the bike when the work was done, so I'll just use this as my baseline I guess.
I appreciate the response.

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2/13/2019 7:56 AM

They almost look like someone was doing some port work and the grinder got away from them and hit the cylinder, kind of hard to tell in the pictures.

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2018 KX450F
2005 KX250
2003 KDX 220
1984 KX 80
1982 RM 80
1980 RM 80
1977 XR 75
1969 Honda Mini 50

2/13/2019 8:43 AM

Does the cylinder look like it has a sleeve in it??? Photo
Photo
Photo

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2/13/2019 9:58 AM

Definitely looks sleeved... take a small magnet to the edge easiest way to know...

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2/13/2019 10:04 AM

DAMMIT....dizzy

Yup...forgot all about that way to check....

Definitely sleeved.

Buyer beware. Do complete engine teardown when buying a used bike...haha.
Funny the shop did a 134 kit on it...

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2/13/2019 12:00 PM

dkurtd wrote:

They almost look like someone was doing some port work and the grinder got away from them and hit the cylinder, kind of hard to tell in the pictures.

Yup, that looks like carbide bur marks to me.......

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2/13/2019 12:02 PM

Yup. Thanks Tracktor.
On top of all that, I've determined it's a sleeved cylinder.
Was not expecting that when I popped the head off.
Surprise, surprise, surprise...

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