Had a customer bring in his Honda HRX476 yesterday. He said it lost its drive and the chain had come off.
Today I decided to take a look, thinking it would have the usual problem of the outer pin shearing on the gearbox output shaft, (had loads of these) and the chain falling off because the gearbox shifting and putting the sprocket out of line.
But this wasn't the case this time. The end of the output shaft including the top sprocket had worn through and dropped off, and disappeared completely. Doh..