Skunkbait,
You need to consider the outer crank seals as well as the centre, namely the flywheel side. My bike's symptoms (starting, getting it off the line) sound very much like yours. Have a read of my experience, hope it is of help.
http://www.nsr250.net/forums/viewtopic.php?t=7023&postdays=0&postorder=asc&start=0

Maybe worth looking for a leak-down test kit, they are useful in diagnosing such problems......http://www.accu-products.com/accu-products/leakdown-test-kit/prod_3019.html
_________________
Rich
MC21 Track Bike / RS250 NF5 'Spencer', NX5 'Cadalora' & NXA 'Aoyama' / RS500 / Two Brothers Racing RC30