dave.owen wrote:It will vibrate without them.
I have a sneaking suspicion it'll vibrate with them too
I'm not over-confident about the Ariel version of the head steadies, I suspect that if the engine really wanted to move about it would make short work of the screw threads that go through the tube ends (which are probably slightly oversize/loose to start with.)
However as I've also seen a number of swing-arm frames fractured at the bottom of the front cradle tubes (at least one of which was on a 650 that might have been running without head steadies) I tend towards the 'don't mess about with the standard setup' position.
'55 Huntmaster, '56 VH, ' 51 VH, '80 R100RT, '00 Sprint ST (but all those Ariel parts can only make one running bike...)