My Raptor has a similar problem while lugging around. I found my problem to be the chain slapping the plastic chain guide. Just for trying, lug yours around and when it starts making the noise watch you chain and see if the noise is consistant with the movement of the chain.

Hope this helps

 

If the problem was noticed after the valve adjustment, I would double check it again. The way I adjust valve is to rotate the crank until the intake is at full open. Then rotate the crank one full revolution 360. That will put the intake cam lobe 180 degrees from intake rocket contact. This is where you adjust your intake valves. Then do the exhaust the same way. This method will always place the cam lobe at opposite from rocker contact point.

If knocking (detonation) still exists, try richening the mixture screw. Keep in mind, one setting will not always be true for both carbs. You can end up with 3 turns on one and 3.5 turns on the other. Just shooting from a hip, try 3.5 on RH and 3.0 on LH. (If one carb is richer/leaner than other, then the fire front can collide in the combustion chamber causing the detonation)

Play with it.

If all fails, gear down.