mine does the same thing, its the sound of the engine sucking in air, remove just the air filter element and see how it sounds, if it go's away install a high flow filter element to quiet it down, you can also do the RAK mod but you'll need to rejet the carb doing that. every stock 650 i'v ridden has that obnoxious sucking noise under the tank that gets louder when the engine is lugging especially in 5th in the lower gears it more of a chirping noise. a dirty air filter will really exasperate it too
dumb bikers don't get to be old bikers
Last edited by pauli466; 05-26-2016 at 04:52 PM.