Swapped one half of a 3400 case with another one due to crankcase seal problems with one half. However I can't get reassembled body to hold pressure. Continues to leak at area next to cylinder where halves meet and its difficult to tell exactly where the leak is. Tried new paper gaskets, even used a thin coat of Dirko HT, as well. Still no luck. Is it possible that you can't switch one half a case? I can't imagine they are machined as a pair but I'm strictly guessing. Even switched cylinders but still leaks. Any suggestions would be appreciated.