Adrian, tapping a barb fitting is a great idea if the cases are apart. The aluminum and brass that will drop in the bottom end from drilling, tapping, and treading the new fitting in will prob ruin the crank or rod bearings. You can try and devcon or jb the existing tube back in but that would be very temporary and could Def cause a burned piston (or worse) when the epoxy eventually fails. If you wanna split the cases and drill and tap a fitting in bring it up and will do it in a few hours