Leaking Bings-Andrew.
Sleepy has the right idea regarding the Bowl.
Make sure the Bowl vent tube is not blocked.
If it still leaking the Carby may be flooding.
If so replace the float Needle and Needle Pin .
The best is to buy a Bing 54 repair kit. They are not expensive.
You get the Needle and Pin, Cork Gasket , Main Jet screen , 0 ring for the Top, Needle Jet Clip.
Also the cable Rubber Boot. Also If the Float is white . Replace with Black Type.
Parts are not hard to find. BING USA, VMX Service Holland, EnduroKlassiker Germany.
Or many Light aircraft use Bings. As they are used on Rotax Engines .Try many of Aircraft Parts
Supply Shops. They also have Kits.