Happened at WOT after 6-10 seconds wot... the right piston's near to have a hole too right at the same place...
I suspect detonation... I ran 50/50 ratio of 91/110 octane last year with no problem and this year I checked compression and squish... 130 psi both side with a non reliable gauge and .050 squish so I tryed only 91 octane and I think it's what caused that...
Other suggestion? 160 main in 33mm pwks at 40-50 degrees 1000 ft altitude
modifs:
fmf fatty's, vforces 3, noss head with 21 cc cut domes, 795 series pistons, 4mm stroker 5mm long rod, fast wood/trail port, port matched case, +4 timing, 33mm pwks, 6'' K&N style pods
could it be cuz i was Lean on main jet or a air leak? Does it cause hole in piston? cylinder wall looks nice no seizure... piston skirt have some scratches but didnt affect the cylinder