Hi,
You could try checking the float levels; clean the float bowls; get a cotton tip (cotton bud, whatever you call them over there) with a small amount to cutting compound like some toothpaste or autosol and very lightly clean & polish the needle seat; and try to get into the practice of shutting the fuel tap. New float needles and fuel taps can be ordered if necessary. Some of the US guys might like to recommend a local supplier for you, or check Tyga's website. Hope this helps.