Yes it keeps the carbon from building in the chamber and if you don't have hardedned valve seats, it will keep you from burning valves. It's a great top end lube too. This fuel nowdays is really dry and I strongly suggest anyone running old iron to toss a swing of it in your tank every other fill up or so.
Is it only really for the older machines? could I use that on a 95 Sporty?
but of course... it's just a small amout of oil, can be ran through anything.... 2 stroke oil has the same advantages, if you do some research on it, people recomment small amount of 2 stroke oil in their gas over any other fuel additive for a happy top end.