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hard hours ridden by AA rider. This looks like blow by? Can you confirm? Thanks 
Hard to read 100% with just that photo, some blow by but..40 hard AA hrs… just do the top end…likley powervalves need a service anyway….
If you ride the bike again and it breaks a skirt I told you so.
I would definitely pull the cylinder and further investigate based on this, good chance the sides will look worse and it needs replacing
Planning on doing a top end very soon. That bike lives at wide open most of its life, but I was still kind of surprised to see the blow by.
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Just curious, why ride a Xtrainer at AA level? Did you do a compression test?
It’s my second bike, main bike is a kx 450. I love the xtrainer once I got the proper springs for my weight. Got stiffer springs and made a huge difference. I’ve got 5th overall on that bike before. Buddies get mad at me when I pass them on it, because they say it’s a “girls bike”. Idk about that it can be an absolute weapon depending on the track. Is it a full blown full size bike?no. But it does a ton of stuff extremely and surprisingly well. No Didn’t do a compression test yet.
Wasn't criticizing, was genuinely curious. I have a couple 300rr race editions and for a AA pace I would have thought the xtrainer would be out of it's league. Everyone says how bad the suspension is when you carry any kind of speed and its a pretty tamed down power output.
How did you break it in? Some promote harder breakin to get better ring seating http://www.mototuneusa.com/break_in_secrets.htm
+1 for hard break-in.
The small amount of blow by based on your hours and riding level don't really seem that bad. Would have to see the entire piston and bottom of crown to really analyze, but "to me" there's nothing of any huge concern with the little info provided. Would highly recommend knocking out the top end asap as others have suggested.
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