So here I am checking my engine after damage that suddenly occured when riding at the top of mountains in Andorra !
A hammering noise: I told myself "it must be fuel detonating in exhaust because of altitude..!" at least I hoped it was.
A few minutes later a hammer sound came out from engine again..this time it stopped engine and when trying to bump start, engine was blocking back wheel !
I understood that it was serious but couldn't understand how the f*** #Z%*/§$ it could happend as I have been servicing and checking more than necessary!

Could cam chain have been braking off letting piston hit valves?!
Could it be starter fly wheel blocking crank?!
Could piston have melted together with cylinder?!
Could it be conrod bending as a result of driving with a heavy loaded bike up the mountains?!

No No and No, it was nothing of this!!

What really happened:
The big(secured!) bolt holding primary wheel on crank shaft and syncro wheel for balance shaft has loosened and gone off !
Separating the balance syncro wheels, the hammer sound was balance shaft hitting crank
shaft, bending conrod in pieces!
It should theoretically never have happend, Yamaha have mounted the bolt with correct torque, and even secured it.
I have never seen this before, neither has my mechanic.
Though it seem to be possible and I'm glad I wasn't in the middle of Sahara when it happened!

The guilty is probably engine break and heavy luggage and/or something else !!

If anyone has experienced the same or has an idea, let me know.

I will definately fasten the bolt of my next ténéré either permanently or gluing it with some lochtight.

The good point is that everything else in engine seems ok, even after my long rude travellings, so I don't really worry about ténéré quality.


Matt