cylinder pics: unusual wear?

'06 yz450f. Im pulling it apart this winter to check condition, as i picked it up used couple of months ago. Previous owner said it had roughly 50 hrs.

It has run strong, but its snowing outside, and im currious, want to learn...

the marks on the sides of the top of cylinder are not what i expected. I havent measured it yet (need my calipers), and will obviously do so, but was just wondering what folks had to say.

I will hone it a bit and clean it up with atf if still useable, but are those marks on top the result of bad bearings or other issues in the cases, or is that normal residue from combustion? Thanks

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you need to measure it. The marks at the top and bottom are normal wear. The specs are listed in the book.

The marks at the upper and lower limit of travel are the result of the rings stopping and starting as they reverse direction; typical. If they disappear in 2-4 passes with a bottle brush hone, it's probably fine.

Read: http://www.thumpertalk.com/forum/showthread.php?p=4380759#post4380759

Check the rings clearance in the grooves.

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