I posted about this before but couldn't find the thread.
Basically the 750 is a DK Special requiring loads of work and parts including a new head gasket. Engine removed, head skimmed, put together and ran fine; except for a big oil leak from front of the valve cover gasket. Apparently it is easy to put these on upside down and because the cam box is not symmetrical, it will leak - well Haynes never said 'owt about it.
Looking at it; the engine would have to come out again as the valve cover cannot be lifted off in situ. I couldn't face that as I've been in hospital having a new valve (heart) of my own so can't lift anything heavy - break the ribs again see. Ask Julie.
So I saw some chappie on You Tube change the gasket by undoing the 14 screws and lifting it up. So that's what I did (see photos if they made it through) and was fairly fiddly including having to remove the coils which was a right pain.
Just ordered a new genuine gasket off DS for £20 (WHAT !!), and will fit it and let you know the outcome.
Cheers
Phil