There’s only one remaining 600cc supersport-class bike that currently achieves Euro4 emissions compliance. So while you may still find GSX-R600s, ZX-6Rs and CBR600RRs in dealers, they’re not eligible for inclusion in this list. The Yamaha’s engine is a direct descendent of the motor that first emerged in the 2006 R6, which was controversially supposed to have a 17,500rpm redline. It later turned out that the rev counters were geared incorrectly, and in fact the motor was revving out at ‘just’ 15,800rpm. Today’s R6 has a 16,500rpm redline, but its power peak lies 2000rpm lower than that at 14,500rpm. That’s still enough to make it the highest-revving bike on sale today.