Random knock on start up
So I replaced my valve cover gasket and adjusted my valves. Now i went riding today with my little bro and i did a donut and i accidently killed it because i was gonna flip if i didnt let off the gas. And anyways I went to start it and it sounds like the valve is hitting the piston or maybe its detonating when i start it, it has 89 octane in it right now and it wont do it everytime i start it but only at random times. The quad runs great and everything but i just want some input from you all.
Btw my piston is either 10:1 or 11:1
2005 yfz450
FMF pipe
G-Force axle
20in fronts-18in backs
Pro Taper bars
Pro armor nerf bars
1998 300ex(built for my sis)
fresh engine
11:1 wiseco piston
full DG exhaust