Missing Power Valve 2001 1200 xlt

[atrauty]

Ski started missfiring, reduced power, pulled spark plug, electrode closed, piece of debris in plug.(#3)
Piston top looked normal, but cleaner than 1 and 2. Bore scope showed slight wear on power valve side, in the shape of the power valve. Pulled head and noticed that PV is missing. Now this is a SBT engine installed in 2011 ran great up until this happened. Pulled engine, took down the top end, no debris in the case seen. PV missing? Where is it, so if it had the clips and such why did the PV make contact with the piston? It's like the PV and most of its shaft just broke off?? Seems like the PV guide in the cylinder is worn more then the others.
And by some strange coincidence just exited through the exhaust.??
trying to decide how deep to go in the repair, cylinders, crank, etc. I suppose I should have pressure tested before I tore it down. Any thoughts would be appreciated. I can post pictures but not from this media.

[SBT-Tech 1]

Re: Missing Power Valve 2001 1200 xlt

This is a common problem with Yamaha's PV engines.
We believe that heat and stress cause the shafts to become weak and snap off.
I am sure that if Yamaha were to make that engine today they would use a thicker shaft.
You can do a cylinder exchange if the only damage is in the cylinders.

[atrauty]

Re: Missing Power Valve 2001 1200 xlt

Ok Thanks for the info. Would overheating the ski add to/cause this stress? As far as the Top end exchange, is there a need to measure and gap the rings on assy, and what position for the ring gaps. Is break in oil needed and the same break in as the SBT Rebuilt engine with the cylinder exchange?

[SBT-Tech 1]

Re: Missing Power Valve 2001 1200 xlt

Ok Thanks for the info. Would overheating the ski add to/cause this stress? Yes.
As far as the Top end exchange, is there a need to measure and gap the rings on assy, and what position for the ring gaps. SBT checks the ring gap, and the ring groove has a pin in it so they only go in one position (numbers on the rings go up.).
Is break in oil needed and the same break in as the SBT Rebuilt engine with the cylinder exchange? Break in oil is not neccesary, but it helps. Break in is like a new engine.