Understand what you say about not wanting to split the casings, but there is much more chance of them been shot than not, 40 year old rubber will be perished so unless they have been changed more recently I’d strongly suggest bite the bullet and tackle them.

Unless you put a screwdriver in the casings to prise them apart (as people temd to!) you won’t damage them, and they will seal again just fine. When apart you may want to consider replacing the main bearings, the layshaft needles, the cruciform and clutch corks if any of these look suspect. Vespa engines really are very basis and parts are fairly cheap, only challenging jobs are removing the old mains (if you need to re-use the crank) and fitting the new ones, I must admit I didn’t tackle that myself and left it to my dealer! IMO these jobs are worth doing now or you’ll only end up doing it later..

My only worry is with splitting the cases and opening her up is that my own technical knowledge of the “inner workings” is a little limited, and therefore prone to make mistakes.

I once had a motorcross bike and had the cases split, new gaskets etc, and no matter what we did – the new gaskets always had a slight leak, now I know thats a different kettle of fish, but I am slightly worried… on the other hand, I get your point about when the lump is back in the bike – I dont wanna be finding out I have serious issues.

oh what to do.. advice ?