The Barry Sheene bike we have here is a square-four 1975 Suzuki RG500 XR14. Sheene won his first ever GP on it and the '76 and '77 world championships.
In the yellow corner is an inline-four-cylinder 1980 Yamaha YZR500 OW48R, ridden by three-time world champion 'King' Kenny Roberts, complete with two reverse cylinders (hence the 'R').
Both are excessively loud, smelly two-strokes, with wafer-thin powerbands and no interest whatsoever in suffering fools gladly.
The Yamaha is tiny, like a cramped 250 and nothing like as roomy as today's MotoGP bikes. I'm a good head-height taller than Kenny Roberts, so it's all I can do to get feet on the pegs.
The motor is far more tractable and friendly than you'd imagine. Combined with its light weight there's just enough low-down power to short shift, but who'd want to do that? Crack the throttle for the first time and wait for the unexpected.
There's a big hole at 7000rpm, which is the calm before the storm. When the needle sweeps round to 9500rpm it just takes off. The madness carries on to the 10,500rpm redline, then it's time to push down on the race-pattern gear lever, slice through to the next cog and let the engine go berserk all over again.
The Suzuki is much roomier. The 37-year-old square four-cylinder 500cc motor still has an excess of oomph and not much weight to push along, so the acceleration is enough to pin you back in your seat.
This RG500 XR14 still feels good on the brakes and sure-footed in the corners and given the opportunity to ride either on a hot sunny trackday, I'd take Sheene's - it's easier to ride.