Noise in top end

[Xitemntracing]

I have an 18 gp 300 with a lectron and rk tech billet head. Bike is new with 100 miles on it. I get a intermittent clank from the top end when holding at 1/4 throttle. plug looks fine ,and bike has the update for the ecu from Gasgas. Head was milled for my elevation ,but is cold here. Have not tried mixing race gas yet , back to 2 strokes after many years on four stroke so need a little advice. Is this an octane problem ping ? timing out? It is freaking me out !