I got the AZ badboyz 250 trail mod kit and ive been hearing a knocking sound when i like accelerate and going up hills its loud. Its not the clutch i looked over that and replaced the clutch buttons and its not the flywheel or starter checked all that. i sounds like its coming from directly under the gas tank or somwhere near. But i dont know what would be causing the noise.

 

Check airbox to see if it is touching anything. Also exhaust system touching anything.
My 2003 400 Trailblazer was knocking at idle and high reving. It was the airbox rubbing on the frame.
Put some rubber pad between airbox and frame to stop noise.
When a quad get older the starter drive will knock.

 

hes right same thing on mine its the air box knocking