just enjoy it, make ppl think you've done alot of engine work to it. i know mine blows black smoke when it starts, but it's gone straight away so i don't worry bout it. like ppl have said just it engine dumping fuel to start it, and with the open exhaust it's coming out faster and doesn't have time to mix with more gases before it comes out.

make sure you dont touch the accelerator when cranking the engine.