If you look at page E14 in the Online Parts Manual, you will see there should be an M8 thrust washer between the pump shaft and the crankcase. This is to prevent the shaft from chewing into the soft alloy. (A cheap production alternative to a hardened steel insert/bearing.)

There is no official seal part number, but there are alternatives that have been used successfully. There have been a number of threads about it already, and you should be able to find some good info with a search.

In fact, try this: http://nsr250.net/forums/viewtopic.php?t=11190&highlight=oil+pump
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Andy.
NSR-WORLD.COM

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