Again.. Not quite right from the pictures, but it's got to be worth checking the rear level sensor..
Item 8 - HEX NUT WITH PLATE - AM6-8-ZNNIV SI
From your picture it looks like it has an antivibration ring round the top of the nut. That's probably not a locking nut which is usually nylon, but in theory it could be reused repeatedly providing the correct torque is maintained?
YAMAHA YZ 85 125 2009 – 2018 REAR SPINDLE NUT M14x1.50mm 90185-14012 TITANIUM GRADE 5 REAR SPINDLE FLANGE LOCK NUT Key Features: Premium quality Grade 5 Titanium (6Al/4V) – the alpha grade of titanium. Superior to other grades commonly used in the motorcycle market. Ideal for high-stress...
YAMAHA YZ 85 125 2009 – 2018 REAR SPINDLE NUT M14x1.50mm 90185-14012 TITANIUM GRADE 5 REAR SPINDLE FLANGE LOCK NUT Key Features: Premium quality Grade 5 Titanium (6Al/4V) – the alpha grade of titanium. Superior to other grades commonly used in the motorcycle market. Ideal for high-stress...
I did rule it out first due to it being the wrong size, but it gives a good picture of the type of nut I think he's found. 14mm AF is possibly a 10mm diameter bolt but M10 would usually require a 17mm spanner whilst an M8 would usually need a 13mm spanner. The M14 would need a 22mm spanner.. unless, as a flanged nut it might only need a 21mm spanner.
having gone slightly off topic and down a nut size rabbit hole, I might not be helping with the original question
Looks like a philidas style of self-locking nut for single use only. They deform and bite into the bolt threads on tightening. A similar but larger diameter nut is fitted to my Yamaha Tmax lower shock to swingarm bolt.
I haven’t seen one used on a BMW. I’ve never seen one come loose either.
Mystery solved.
It's from the top of the fork.
My bike had the ignition button replaced and the top yoke has to be removed to fit it I'm told.
A bit careless of the technician, but not as careless as leaving it of completely i suppose.
They're a single use nut.
Thanks to all for the help with this.