Do Series A singles have sumping problems?

[BigEd]

My Norton 650ss fills the sump after about a month of sitting, then starts to leak profusely from the top of the crankcase. I have looked at the anti sump ball valve with ignition cutout, but it still seemed a bit risky should the switch fail and allow the engine to run without first having the oil supply turned on.
The plan is to make a valve which uses the 650SS igntion key as handle. When the valve is in the on position, the key can be removed, when the valve is in the off position the key cannot be removed from the valve. I only have two keys for the bike and only ever use the one, as the spare is taped solidly onto the bike in hidden spot, so I think this antisump valve will be without risk. All the bits for it are in a small box, the machining is mostly done, just need a bit of time to complete it.
Glen

I have seen a bike fitted with a tap using an extended handle. The tap was fitted on the feed to the oil pump in such a position that if the bike was kick started with the tap in the off position the kickstart lever pushed the tap to open. I think this may have been on a Norton twin but could be installed on many makes. It would be automatic but not foolproof as the bike could still be push started or (possibly) electric started without the tap being opened. It would not be feasible on some machines because of the layout of the oil feed pipes.