@GiannisT The smart thing to do would be to tear it down and inspect/renew where appropriate. There is no shortcuts, one way or the other that engine is coming apart. If the swarf hasn't contaminated the main bearings it'll no doubt have damaged the big end bearing. Anything short cut you do will likely cause further harm and stress to other components causing bigger, more expensive, problems in the long run. That bike didn't die on tickover, going by the extent of the damage to that piston/head.
The head needs throwing in the bin, it's trashed. You might be able to get a tuner to alter the squishband and remove the detonation/debris marks from the head, but as it stands it's a glorified paper weight.
The problem with running damaged heads such as that, is that it encourages detonation, even if the jetting appears to be correct. In other words, it's just a shortcut to a blown engine, doubly frustrating when it's freshly built.
My advice, don't scrimp on critical components, it'll just come back to bite you.
You could spit the cases and inspect the components for wear. If all is in order then you may not need to renew (although I would anyway).
You could just inspect it in situ and see if the float is okay and if the big end bearing is damaged by checking for play. No way to tell about the mains or crankcase seals without tearing it apart. If debris has contaminated the seals then it will never idle/run right.
