I have a 2006 DVX 250 that I have been attempting to rebuild by myself for a while now, it's all together and it will fire up but will run very rough and it sounds like it has spark knock randomly, it will start up and run rough on half throttle and will periodically die down and make the noise of spark knock, I checked to make sure the spark was working properly during the noise and it was. Its in timing correctly, it has plenty of compression, the carburetor has been rebuilt and cleaned but it still won't even idle or run right. It will "idle" If I crank up the adjustable idle screw on the carb but it will still bog and make the sound after a while and die. I have no idea what's wrong with it. I have a video on it dying down on YouTube:
https://youtu.be/HxoEjeejVdk