Thanks to all contributers to my original post. Several of you have agreed that draining the carb is one solution and this concurs with discussions I’ve had elsewhere. But why? What changes to fuel in the carb which doesn’t change when it stands for the same period in the tank? I can’t fathom it out and while I happily accept the solution I would like to understand the chemistry of it. And why only on the Skorpion?
Thanks to you all