Have finally got the A10 propery up & running and it's going very well. However, when cracking along (say 70mph) there is a noise that sounds something like a blowing head gasket from the near side. It disappears at low speed / standstill which of course is the only time I can put my hand / head down there to feel for it - no sign of gas escaping. Compression is excellent on both pots.
However, what has just struck me is that I understand the engine breather exits from the crankcase just behind the primary chaincase. Could it be this making the noise?