I have a 2000 YZ125 that will bog and die when the throttle is quickly opened. If I roll on the throttle it does not bog and I get some wheel spin and good acceleration. This problem just occurred, the bike used to run fine. No jetting changes were made. This problem shows up every time when the bike is being ridden. Sitting in neutral it will occasionally do it when I rev the engine hard. I have checked the power valve (in the cylinder) and it moves freely. I left the power valve cover off to observe the linkage when the motor is revved, it doesn’t seem to me to be moving freely. When the motor is revved, it sort of clunks up and down. When the motor bogs, the linkage does not move. I am unsure if the power valve governor is supposed to move the linkage smoothly or clunk it up and down. I’m also not sure if the bog is related to the power valve governor not moving or if something else is causing the bog and thus the power valve governor doesn’t move. I’ve completely disassembled the carburetor and cleaned it. It has stock jetting. The compression is 120 lbs. I’ve run it without an air filter or silencer and it does not make any difference. I’ve changed the jetting (leaner) and it doesn’t make a difference. I’m out of ideas, any help would be appreciated.