Do you wonder about the 90 in the name of the bike. 90MPH. I often take mine to 75 and soon to push to 80. On a privet road of course ( wink ). Has anybody gone for the 90.
There was a road test done by Cycle World in 1963 on a BSA B40 ss90 on a new bike and it did achieve 90mph at 700rpm. But on a bike of that age now I would not consider even trying to get upto that speed you are asking for serious trouble.
yes its a worry, but a few seconds off the 80 mph speedo, WOW.