Ninja 1000 ABS - after 60,000 klms had to change both sprockets and chain, socket size = 27mm, tried undoing with 1/2" impact drive, wouldn't budge, then tried with breaker bar, wouldn't budge, got hold of a 27mm single hex and a heavy duty impact driver, just spun the nut off with no effort. Helps when you have got the right tools.