MOT time for one of my airheads. I haven’t used it for best part of a year. Fresh fuel, it had been drained including float bowls and battery had been on tender. It started right up but immediately I felt something wasn’t right. It sounded more like a big single even though it was firing on both and revved up cleanly. A quick test ride and performance was ok. So basically quite strange as ‘ it ran well before being stored’. After a Head scratch( page 3 in the manual of what the hell could have gone wrong) I remembered that I’d taken the tank off to replace the crankcase breather valve). What could have been disturbed? Yes! The throttle cables. One had come out of the junction box and the carbs were consequently out of balance as one butterfly was open at tadge more than the other. Free play readjusted and back to being smooth as silk .