I think the G91 is stelite welded for hardness ?, Where it touches the pushrod ?,
Also the ends of the pushrods should be hardened ?,
I had this trouble 40 or 50 years ago, But not had it again, Strange !,
I wonder if there was some soft ones around in the old days,
But with a bit of Copperslip and the 1/4" roller it's been fine,
The Vincent Clutch should be light ?, And I try not to leave it in gear at traffic Lights,
Also now the mod' I showed you with needle rollers should make even less friction ?,
A case of lots of small things ? To improve the ride.
Good Luck, Bill.