My Motor siezed at track day

[du907]

I was riding my 92 907 at a club track day and the motor siezed about half way on the FIRST lap. I was going about 100 mph and the motor quit like someone hit the kill switch, then the rear tire locked and started sliding back and forth. I pulled in the clutch and the bike straighten right up, I coasted to a stop. After bring the bike home I started to look things over. I started to remove the left side cover (the cover with the water pump) and it normally just pulls off, not this time. I used a steering wheel puller on the main shaft and finally got it to break loose. The alternator rotor had melted and seized to the stator which is in the cover. I have metal shavings all over the inside of the cover. Upon closer inspection, I have deduced that the rotor cracked right down to the shaft. This would have made the rotor larger in diameter and would have eliminated the very small air gap that is suppose to exist between the rotor and the stator. The two parts made contact and wore on each other, creating friction and making the parts melt together causing the alternator seize and stoping the motor. I have 50,000 miles on the bike, but it has been well maintained.
Comments, suggestions.
Bryon

[enzo906]

when was the last time someone worked on it? did they torque the nut correctly?
I just put my PASO back together and discovered that some mechanics torque this nut up far too much (they use the rattle gun on full for several seconds rather than a torque wrench.)

Being the rotor is aluminium and has metal inserts I don't like the thought that it may be overtightened. I had all kinds of trouble removing that nut and the tab washer behind was heavily deformed from it being overtightened. I don't think the revs the motor does would cause a failure.

Where too now. Wreckers? Ebay?. or just see if a new one out of a monster fits?

sorry can't help more. But if you recently had work done I would lean on the place that did it.

[Finnpaso]

Remembering now, that u can put rotor "right way" and also 180 degrees wrongly "inside out" and then rotor is not right way to make power to rectifier/regulator. I allways mark with pen, what is "outside" of rotor. Have that left side been open ever in Your bike? Sometimes regulator failure brokes also stator, but newer heard that rotor.... :ugh:

[du907]

The rotor has never been removed. That side of the motor has never been work on except to fix a stripped bolt. I plan on cleaning up the metal shavings, putting some motor flush to thin down the oil and change the oil and filters a couple of times after running the motor a few minutes to wash the particals down. Plus I will have to take the bearings from the water pump and the cover out to get any particals flushed out of them.
du907

[Finnpaso]

VERY, VERY intresting problem...

[du907]

Does anyone know which way the nut that holds on the rotor and flywheel is thread, right on, left off, ( regular) or reverse thread.
Thanks
Du907

[Finnpaso]

Its normal thread, but near allways locked with Loctite and its very tight...