‘ The YPVS had the best motor’
“The YPVS is my favourite two-stroke motor. It’s a wonderful engine and is the last in a long line of Yamaha parallel-twins that started aircooled way back in the 1950s and culminated with the liquidcooled RD350 YPVS in 1983.
“Before the powervalve, two-stroke motors were getting peakier and peakier as engineers squeezed more power from them, but when the YPVS arrived you suddenly had a lovely spread of power on a two-stroke thanks to that powervalve.
“Powervalves were around in sophisticated race engines before, but Yamaha used it on a road bike to create a broader spread of power. On a two-stroke the powervalve lowers the top of the exhaust port by about 10mm, which gives more mid-range, before opening and raising the top of the exhaust port, giving a topend boost, too.
“And instead of an on/off system like its rivals had, the YPVS did this progressively by working off sensors in the engine and setting the valve’s position to certain revs, giving an elegant and refined power delivery. It was bomb-proof, too – which some of its rivals certainly weren’t.
“It really is a fantastic motor and my favourite two-stroke engine ever built.”
Powervalve gave improved flexibility