broken crank case bolt

[ridemore]

I was wondering if anyone has had this problem before. It looks like it's the bottom crankcase bolt and the nut looks like it was sheared off. I bought the bike last year and don't remember seeing anything missing in the area, but can't be sure if I even looked to see if the nut was there. I guess my concern is whether it might be a bigger problem or possibly a one off type of thing. My riding style is mostly commuting and some windy roads but no off road.I am a bit on the bigger side but I don't think that my weight could break that bolt.

[ridemore]

Sorry, the pic is pretty bad. I hope these explain a little better. The one with the arrow is pointing to the bolt that has slid out, and the other is the hole where the bolt was which is behind the LH foot peg. I wonder if A) the bolt is going in the right direction and B) could riding have sheared the nut off, or something else maybe and could it happen again.
Attached Thumbnails

[oslin]

Mmmm, that's an odd one I can not say I have seen or heard of that before, are you sure the nut has sheared off ? or has it just come loose and dropped off, there would have to have been a lost of force to shear a bolt that size and I would of expected some other damage or trace if that had happened unless the bolt was faulty with a hair line crack for example, I think I would be inclined to replace the bolt and put the nut on with lock tight.
sorry that is the best I can come up with at present.

[ridemore]

I got it out and this is the other end.

[oslin]

That does look like a clean shear from what I can see maybe it was over tightened ? anyway I would still replace it with the correct bolt or even a high tensile one and see how you go, I am sitting here trying to think why it would shear, it is not taking a variable load so it is very odd and it still could be the wrong material you would not know unless you had it stress tested,
also it is an odd place to shear normally bolts of that size would shear at the base of the thread not next to the nut ?
Keith

[ridemore]

That's kind of what I was thinking as well. I will replace it with one from the dealer and make sure it's torqued correctly and double check it I'm sure every time I walk by the damn thing.

[oslin]

Good luck with that and let us know if you come across any other information/observations
Keith