Yeah, in the 50s 140 mph was 'going a bit' - it wasn't until 1979 that I had a bike that would do that - a Yamaha FJ 1200.

Bill, I would have said a YDS1 was more than 'reasonably fast' and yes, they did rattle - weren't in racing fettle until the pistons were slapping well. By the time I got to ride one they were up to YDS7 and the YDS1s were getting on a bit. Did focus the mind somewhat when that 250 hit the power band... and you were listening to every noise the engine made in case it was considering nipping-up - always happened as you were dropping into a turn. Had a good supply of leather patches for my arse though.