Triple 500cc world champion 'King' Kenny Roberts took to the Laguna Seca circuit on past and present grand prix machinery on Thursday.
Roberts rode a contemporary 800cc four-stroke Yamaha M1 as well as his 1980 500cc two-stroke, which he took to his third and final world title (see below for further pictures).
"I'm glad I came up 30 years ago! I was in the right era," Roberts told the official MotoGP website after his Thursday ride.
"In my day if you were within a foot of where you wanted to be - great.
"But with these [modern] bikes you need to be millimetre perfect.
"That's why the racing is so technically close, but hard to pass. Everything has to be so precise.
"The bikes are very rigid and the tyres have a lot of grip. It makes them very hard [to ride]."
The American legend won 22 races during his grand prix career, but never got to race in front of his home fans.
As part of Yamaha's 50th anniversary of road racing celebrations, Roberts will ride demonstration laps over all three days of this weekend's US Grand Prix.
Present Factory Yamaha MotoGP stars will race in a special red-and-white livery at the event.