Just bought a 1000 Fazer

[Falcon 269]

Hi and welcome.

Where did you buy the bike ... from a dealer or private seller?  Either way, if this has been happening since you took delivery, it's their responsibility to fix it or give you a refund.

It sounds like it could be a fuel supply issue but we need more information.  What's the mileage?  Any mods to carbs or exhaust?  Has it been standing around for a while or was it ridden regularly?

Have you tried applying a little choke when the motor is warm to see if it revs without trying to stall then?