The Express SR uses the same engine as the Urban, just so you know.
Anyway, the brake shouldnt need to be on for the bike to start. So long as the engine spins and you get spark, that means the bike doesnt care what the brake is doing.
I really hope you've cleaned out that carb like you've never cleaned before. It makes a huge differance.
And yes, the bike should start up just fine with a dead battery so long as you use the kick starter. Though if you like you can connect a 12v car/motorcycle battery for the time to test stuff. The electric starter's a lot easier then the kick starter after awhile, so long as you dont burn it out from overusing it.