Aprilia RS50 gear selector shaft spins 360°

[LewisM]

This morning as i was trying to bump start my bike i hopped on and shifted in to neutral from 2nd. The bike went in to neutral and i pushed it round for my 4th attempt to bump start. Went to shift in to 2nd with clutch pushed in and the leaver just spun about 45 degrees. I stopped and investigated as i could but was late for work and saw that the shifter rod is just spinning all the way around. Any suggestions for whats gone wrong as i only understand plant vehicles. Not little gearboxes on a bike . Thanks

[barrkel]

The gear lever works ultimately by rotating a shift drum in a ratchet fashion. The shift drum in turn has grooves in it that control the movements of selector forks, which in turn move gears around causing gears to lock via dogs and slots.

This picture has the shift drum on the right hand side, and shows the selector forks between the drum and the gears: https://i.stack.imgur.com/kEG5S.jpg

Sounds like the ratchet mechanism is broken or disconnected somehow. I expect that would need splitting the engine to fix, but I don't know for sure.
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Bikes: S1000R, SH350; Exes: Vity 125, PS125, YBR125, ER6f, VFR800, Brutale 920, CB600F, SH300x4
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[Nobby the Bastard]

Or it could simply be because the bolt that holds the lever on has come loose
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trevor saxe-coburg-gotha:"Remember this simple rule - scooters are for men who like to feel the breeze on their huge, flapping cunt lips."
Sprint ST 1050

[LewisM]

After taking a closer look in the light i realised only the selector was worn. After dismantling it i saw that the teeth inside were worn to bits hence the slipping. I will be ordering a new selector in the morning. Thank you very much for the help!