Hi
Being stood for so long my guess would be blocked jets in carbs
Had similiar problem with rough idling I removed spark plug cap on number 3 and no change to engine running removed any others engine died turned out to be blocked idle jet
Being stood for so long my guess would be blocked jets in carbs
Had similiar problem with rough idling I removed spark plug cap on number 3 and no change to engine running removed any others engine died turned out to be blocked idle jet