sprockets falling off

I bought a brand new r6 back in 03. About a 2-3 months ago when changing oil I found my counter shaft sprocket had came off. There had been no mods or maintenance to this part of the bike. This was the original set. All I found was the nut. So I went to the dealer and ordered a lockwasher. When I tried to install the old nut with the lockwasher, it would not torque properly. So I went back to the dealer and ordered a new nut. I installed new washer and nut. I folded the tabs on the lock washer, but last week, I found it had came off again. When I went to the dealer ship where I bought the bike, they said we don't know if yamaha will do anything because it is out of warranty and it has 27000  miles on it. I understand what they are saying but this is defect from factory and not a normal wear failure. It should not be able to come off even if it had triple that mileage.I wonder if anyone has any dealings with this or similar problems on their bikes? The dealer in my hometown is going to work with me. Anyone have any connections to Yamaha? Maybe if you do you can hit them up about potential problems since this is a safety issue. Thanks to anyone who can be of assistance.  

Weld it!!!!!!!!!!  

thread locker. Almost the same as welding, but can be gotten out later on.

With a LOT of force.

~Keager  

Try locktite red. You can always apply heat to melt the threadlocker if you need to remove later. Are you SURE you installed it correctly? Can you post a pic?