According to Stewart Roy of SRM, all BSA's valve seats were soft from new. I suppose he knows what he is talking about. With this in mind I may consider his hard valve seat modification as an insurance policy, while I am rebuilding the engine.
Rowan
Don’t listen to sales talk, as Mr 54_A10 said in a less kind way.
Better “insurance” is not to disturb valve seats that are obviously secure in the head.
One of the nice things abut being an Ozzie is you can say exactly what you mean and not go tippy toeing around with inferred meanings.
SRM did a blatent and unforgivabale con job extracting thousands from confused BSA owners that if done today down here would have them up on fraud charges.
And yes seats are best left alone.
More damage is done by idiots with seat facing gear they don't know how to use than unleaded ever will.
However if you are worried, measure you valve lash , at the same time of day over a period of years and I will guarantee it will get bigger, not smaller as would happen if the seats were regressing.
