For any stroker the plug condition will tell you an awful lot about what's going on.
When you put the bike away it might be worth while checking the plug condition and also when you try to start it up.

Riding style, plug grade and type, fuel and oil type could effect starting as well as more sinister potential issues like a crank seal on the way out - could be weeping tranny oil into the crank case when it's not in use (I'm not intimately familiar with the NSR V twin but this applies to any performance stroker) or, you might need to service your carbs and perhaps fettly the pilot jetting to suit the starting.

At any rate, more info would be needed before you can start pinning down the problem.

J