There is nothing wrong with the priniple of fitting cylinder liners. What most of you may not appreciate is that Erik’s Premierhas a ONE-PIECE
cylinder – the head and barrel are ONE casting.
All these early side-valves get very hot when they run and the differential between the sleeve and the outside of the barrel can lead to it cracking – you end up with a “detached” head, which is what happened to the Bradbury.
It is quite normal for even the best veteran barrels to crack across the ridge between the two valve seats, I have known it to it happen to several Triumphs (and they are the best of them – in fact I have a theory that Triumph, Rover and Premier barrels were probably all cast at the
same Coventry Foundry).
I would quite happily use a liner in a normal barrel – have done in fact – but don’t ever do it with these early ones!