i have recently rebult mine.

mine was also a tw*t to start and it just did not like the throttle being touched at all until it had been running for a while, once going it was ok not the performance i was expecting.

Mine turned out to be the centre seal, the outer o-ring was ok but the bearing and presumably the seal also were shot.

Just as a comparrsion, when i bought the bike it took 10+ kicks to get it going, then only bumping would get it going, then i got fed up and after investigating decided a rebuild was in order, it needed the top end doing too.

I started it for the first time last night and it fired straight away on the first prod of the kick start, I've owned a lot of twostrokes and this has been the first with a crank seal failure, i'm no expert on nsr's but the only other bike I know that suffer from crankseal failures are the vj23 rgv, that also have an integrated seal in the bearing rather than a labyrinth seal.

What your saying about your does seem to point the same way