I've been raving about a problem on the UK site with good suggestions from folks there - I hadn't been able to identify if fuel or spark was the issue until yesterday............
OK - found the problem -
I had failed to mention that the sssttuutttter only seems to happen when the tank is getting close to reserve - and yesterday the problem occurred long enough for me to identify that it was indeed fuel (cooler exhausts on 3&4)
So - I have Pingel fuel taps and the way my fuel lines have been routed to the carbs has allowed an air bubble to form when fuel is low...............
HURRAH!!
now to re sort the fuel lines and thanks for your input fellows
Bryan