Hardened valve seats and valves
Given that the automotive industry and the petroleum companies care nought for old bikes or cars, and put allsorts of oxygen containing compounds in their formulations for emission control and injection systems. And may go even furthur in the future on formulation,You can use additives to mitigate the effects of modern fuel on valve seat recession, or even modern two stroke ashless oil. But the valves sold by Vinparts are made by a Formula 1
part manufacturer are are a better shape than the originals with regard to flow.
You pays your money and make the choices, also the time to get the job done is now, I speak as an independant observer and have no commercial interest, in any spares manufacturer. If you use the bike for short distances and keep off the freeways and motorways , don't use them much, them the additive should suffice. I have bought a set for a 636 Comet currently in a foreign land and in the process of being fitted for the same. If i should live so long.