[jambo]

plenty of fuel getting through to both carbs? (check there's still lots of fuel in the tank, then see if you can get to the carb drain screws and see if fuel flows out of both looking like nice clean petrol.

If that's good, check that the connections for the battery and other electrical components are tight.

That said I'd be checking Dizzy's idea about the choke before getting too involved in anything else as the SV's got a bit of a history with sticky choke cables and choke plungers.....