That looks much more like an issue of too much timing for the fuel he was running.
As a general rule, a lean tune will torch the center out of a piston, while a rich one, or detonation, will attack the ring land area first. The ground strap on the plug being damaged is one clue for detonation as well.
Hopefully your buddy gets some resolution from the shop who tuned it for him.
They can detonate from to much timing, bad gas, or being to lean
I think it was the first that did the damage
The motors are equipped with knock sensors but something to do with the pitch of the blower whine trips them off all the time, so they are disabled in the stock computor.
Coolness list by 90cr500guy
Bob's = 50/50
Cepek = cool
Solidbro = cool
Brit = loser
Stoffer = 1 up from Brit
MFDB = cool
Danny = ok
I shattered a ring land on a hyper-u piston from too much timing on too low octane running too much boost! I was totally working that z06 until the smoke...
yeah, a lot of people forget about timing and pump gas and try to max out the timing and rely on knock sensors. I didn't have a knock sensor setup for my SDS setup, I have ears after all and if your at risk of pinging, your running too much advance for your octane level anyway.
'09 kx450f 4-Poke
Gen-4 trail bike --SOLD--
Gen-3 badass trail/mx bike --SOLD--
Gen-1 built dunes bike --SOLD--
'05 klx110 --SOLD--
'95 pw80