Yamaha YZFR1 and YZFR6

Funnily enough the problem here was virtually identical to the issue that hit the YZFR125 a dozen years later (in 10th on this list). The sidestand switch bolt could come loose or fall out, making the switch inoperative and allowing the bike to be ridden even if the stand was still down. A new set of nuts and bolts solved the issue, so at least it was a cheap fix for Yamaha, even though it was spread over nearly 15,000 bikes.