It's more than likely a piece of the 3rd gear dog that has broken away. I guess it broke off a while back and just sat harmlessly in the sump and when you went over the speed bump it got dislodged and trapped. Luckily you were going slowly at the time.

You will have to replace the offending gear and check the stopper lever arm and its bearing which are the root cause of this particular problem. What happens is the positive stop gets sloppy allowing two gears to be momentarily selected at once causing the weakest part to break - namely a dog on 3rd or 4th gear (usually 3rd).

You're quite lucky as in quite a few cases the crankcase has burst open.

Anyway I hope it all goes well.

As for photos, upload to something like Photobucket then paste the direct link to the stored image in the [ IMG ] tags from the "insert image" button of tool bar when creating a post.

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