18 XC300 possible detonation

[TGM_OFFROAD]

Hey everybody I have an 18 XC300 that I recently had to rebuild. I had a leaky left side crank seal that caused a lean condition and melted a hole in the piston. I just finished the rebuild and I am noticing what to me sounds like some detonation at about 1/8 to 1/4 throttle when holding it steady. I also notice it every once in a while when chopping the throttle. It is just a singular knock. I currently am running with an RK tek head supposedly set up for 91 octane, lectron carb which is adjusted slightly rich with a 4-2 metering rod. I am really paranoid and don't want to have to rebuild my motor again and am kind of lost on what to do other than run race gas which I havent tried yet. Is this possibly caused by ignition timing? I didnt see a way to easily change timing on the bike and there is nothing in either manual about it.