Just though i would post a bit of garage excitement from this afternoon.
16H finally back together after sorting out an array of shortcomings and started for the first time since reassembly - at last Just the new wiring loom tidy up and fit.
On shut down I noticed a drip of petrol, touched the offending petrol tap and it fell off!! Gush gush goes the petrol. A brief mad scramble and disaster averted, thank goodness it wasn't on the road at the time. I as hoping to do a short lap tomorrow.
It was an old spare Commando one and the threaded portion sheared off. Must have overtightened the lock nut i suppose.

Oh Crikey Iain ! It could be that a Commando tap isn't designed to cope with the 16H's vibration levels.

I sheared a 'BAP' tap on one occasion when I didn't really follow procedure and tried to twist the body back as I tightened the lock-nut. Did yours shear right at the end of the thread ?

It broke at the top of the lock nut, flush with the underside of the bush in the tank. It had seen a good life on the Commando before being confined to the used spares bin so probably rather tired in general.
Although it didn't get used i am now feeling even happier about fire extinguisher I bought a little while back.