There are many ways to upgrade the Parallel Twin engine. One of them is realizing an external oil feed as Arthur van Till did. He didn’t weld small mayfolds to the top of the cilinderhead like Mototrans did but he used the left hand cam bearingcover. To make sure the oil reaches both camshafts he made a connecting piece as well. With this “easy” way you don’t have to weld directely to your cilinderhead. The downside ……. you still have to block the oil ways inside the engine.