We machined and bent two two pieces of tube so they would end up in the top of the oiltank, above oil level. Both were welded to the "ceiling" of the oiltank to prevent vibration cracks from happening. Obviously they still allow air in and out. The idea is that air with oil from the crankcase breather goes into one tube, the oil remains in the tank, and the air can get out the other tube

There already was a small diameter breather tube on the oiltank, that has now been removed. Aad leaded the area around the welds, and then we pressure tested and thoroughly cleaned the tank. The magnet in the drainplug did it's job well, this was all just from the drilling and welding, it did not come from the engine oil! We dried the tank and refilled it with oil, then started the bike. No more oil blowing out, on to the next issue, the leaking primary cover....