Ralph's right. The Leak may also be caused bu a tube that isn't cut properly. For the Festo fittings to work well, the tubing has to be cut square. If it's cut at an angle, it more prone to leaking.
Ed
ORIGINAL: Turbulence
The engine has some festo connectors under the front cover remove the screws and make sure the Fuel and lubrication line are inserted properly. While it might be fine to fly with a small leak on a Roo with an opne installation, if you have an enclosed installation you are just asking for a fire to happen
Turbulence