1260S, 4000 mile bike, 3rd gear 35mph, opened the taps to pass a car, surge of acceleration and then the power just flattened off. I was convinced the clutch was slipping. Bit odd, never happened before. Changed to sport mode and tried again, all fine, back to touring mode again, all fine. Anyone had this? Exhaust valve maybe?
Sounds like sticking exhaust valve to me. Take off silencer and see if the valve cycles on ignition on. You may be able to check with a torch in the garage without taking the silencer off though I've never tried this.
