11 Pro with new motor

I don't think there are certain serial numbers creating issues, I think it's more of a piston skirt issue across the spectrum. A new motor with 600 miles should be fine. Just be sure you always warm your sled up to 120degF or so before going hard. Most of the issues I've heard/read about were around 2000 miles. I had a buddy lost the top end at 2400. Seems like that's about the sweet spot for these motors. If you're really worried there are a few companies that sell aftermarket pistons and piston/head combos and haven't heard of any issues after installing those.

Check compression, if both cylinders are within a few pounds of each other and at least 110 or better should be ok. I would highly recommend a piston fix kit of some type, several to choose from you need to make your own choice on that, I dropped a skirt last year right at 1600 miles, don't wait it sucks towing out from way up!