So I went riding this weekend and bike was running good but on a long straight away I noticed a brief knocking noise. The noise occurred after a wide open run in 5th gear down straight away. After the bike topped out I got off the throttle and was flipping the throttle just to keep the cylinder lubed up. About the second and third "throttle blip" I heard a very audible knock in the engine. I'm not completely sure what the noise was but it sounded very similar to rod knock in a car. Only did it those two times and at very low throttle opening. I got back into the power-band and the noise went away. I did mix a gallon of fresh gas with some gas that was about 3 weeks old so I'm hoping it was just pinging but I'm thinking it could of also been piston slap or rod knock. After the ride as I was letting it run out of gas I did notice the engine seemed a little noisy but it seems that is common on the yz250. Does this sound like pinging or is my old engine getting tired?