I'm no NSR expert, but is it fine with the choke on from cold? If so, could it be a bit lean on the pilots? Maybe check that either isn't blocked at all and maybe try tweaking the air screws in a little to richen it up at the bottom end. As a general rule though strokers don't tend to spend much time at all below 3k on the tach other than for a moment in first when pulling away (My TZR 3MA for exampkle doesn't even register revs below 3k - there are simply no numbers on the tach below '3') - and even then you'd tend to use the clutch to keep the revs up a little, so maybe it's just the way you are riding it if you're not that used to strokers? Maybe try giving it a few more revs when pulling off?

If it's genuinely a problem I'd certainly be starting by checking carb basics like blocked jets, unsynched slides etc.

Cheers

Wb