top yoke bolt failure

brought my bike out of hibernation yesterday connected up the battery pressed the button and it burst into life sweet as a nut

off I went down the bottom of the road stopped at junction and the bike cut out now this is where it gets interesting usually when I haven't been out on the bike for a while I take it out and give it a bit of stick and I had every intensions doing this nice day and all

press the starter button a few times nothing thinking it might be fuel I tipped the bike over to the right stared to lift it back up and the bolt that holds the yoke on to the frame brakes clean off

more than lucky or what
now a few years ago I came off the bike and this bolt got bent but I replaced it and the bearing could it be down to over tightening or some other reason
has anybody had experience of this I've searched the forum and cant find anything

Chas

Has the bolt broken, or have you pulled/stripped the thread in the frame.

broken clean off threded part still in the frame

chas said:

broken clean off threded part still in the frame

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Feck me !

Is this broken one a stock part,or one you`ve made ( or had made for you ) to avoid paying BMW prices ??

The reason I ask is that I can imagine something non standard snapping if it isn`t high tensile or heat treated correctly,but I can`t imagine the stock one doing so.
Mind you,there`s no reason why the factory couldn`t have made a few dodgy ones......


P.S. At reassembly time,check the integrity of the thin lip under the top yoke....at the bottom edge of the bearing area....
Mine had torn away following my crash.....I think the idea being that this fails rather than the bolt thread ripping out of the frame.

replacement bolt and bearing bought from m/works couple of years ago done about 20000 miles since then
I don't do any off road stuff or wheelies only thing I can think of is I've over tightened it
I've seen some piks of people doing some serious off roading on this site if thair was a fault it would have surfacd before now

chas said:

broken clean off threded part still in the frame

Click to expand...

Have you got the broken part ?
If so it should be reasaonably easy for the trained 'eye' to see from the fracture the most likely failure mode .
If you are interested I can get it looked at our meterials lab at work , but you will need to send the part to me
If you interested PM me

thanks for the offer pomm001 wont make much difference its a 1998 bike not as if I can claim warranty
the unfortunate part is the yoke dented my tank the rest I can screw back together just thought id let every body else know about it as I said I think I've over tightened the bolt
doesn't bear thinking about the consequences if I'd been moving at speed