Hi Kevin and thanks for the ‘heads up’. This is the first answer I’ve received, and it does help. I have her booked in for a full service in a couple of weeks. There is, it seems, air getting into the exhaust system somewhere. The engineer who’s going to look at her will also check the carbs thoroughly. Hopefully that will sort the problem out. She runs well enough, even now, but the exhaust has to go anyway. Ugly thing on such a great looking bike and sounds horrible. Anyway, thanks again and I’ll let you know what’s found.