I agree with Muskrat about octane ratings, but is Ethanol a consideration Johnny? Most 95 octane here in France (and elsewhere?) is now "E10", ie 10% ethanol roughly. Loads of quite scientific/chemical reading out there if you can be bothered.
Depending on what or whom you believe, the stuff rots fuel lines and can eat some bits of carburettors.
I've replaced most of the fuel lines on my bikes in recent years with modern, whether as result of the new brew or not I don't honestly know - but they had gone mushy/rotten from the inside and bits were blocking filters. No carburettor parts have been eaten as far as I can see.
Anyway, whether out of paranoia or for better reasons, I use 98 in everything old nowadays unless there isn't a 98 pump on a forecourt.
Haven't had pinging problems myself, but I don't have anything higher than 8.5:1 these days and my A is bog-standard iron Flash-spec. A highly tuned twin of another marque, running at 10:1+ at one time, was fine on 98 at standard ignition settings. A lot of it must come down to cylinder head design I guess.
Super Rockets etc seem to me to be a bit more sensitive to pinging than some other engines of similar compression ratio. I am influenced by the findings of Orabanda (published on here) regarding optimal ignition advance/power after extensive rolling road tests. Less than 'book' max advance seemed to work best, advice I have followed ever since.
Cheers, Bill
