Mine sometimes sounds like 'this' after the ignition is turned on and the flap has done it's open , close, open cycle.
Do not hear it after the engine is started though and it does not happen everytime.
Flap is not sticking and cables seem free enough.
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My bike makes exactly the same noise, but it goes away when I put my earplugs in. I just ride it if anything goes wrong thats why we paid over the odds for BMW assist
Alarm is under the silver plastic cover under the rear seat.
This is the stepper motor, near the left footrest, for the exhaust flap and when it happens on my bike, it logs a fault code.