The condition of the crank cases is very important to crank life I think. Quite often you can see damage to the bore face of the main bearings. The bore dia does tend to open up allowing the main to move. Once the main bearings start to give up the balls tends to skid in the race rather than roll forcing the outer race to move in the crank cases. This is where the damage to the locating pins happen.

We also forget that the helical primary gear on an NSR tries to force the crank left all the time. Not good for the crank or cases.

As with piston rings I'm anal about cranks, my F3's gets rebuilt every 1500miles keeping it in tip top condition. My reward is not one single failure and a very smooth non crank cases eating engine.

As far as I can see even before main bearing play can be felt the bearing is toast. It only takes one ball to skid once to cause damage to the race and that bearing is on a one way slope.
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If I have to take the carbs off once more...