i remember reading/hearing somewhere that the motivation paper had a 75% requirement as a minimum. If you get less than that you fail S1 tests, even if you ace the diagramming, cubes and numeracy.
don't ask me for a reference for that though - i think it may have been the nice HR lady on the day.
as for the other 3 tests, I think they'll be looking for a mixture of speed and accuracy. No point answering all 50 questions if you get half of them wrong...
I was also under the impression that the pass mark came from all the tests they'd given previously. ie. they get the spread of marks and take the 90th percentile as a cut-off point.
-A