adam bike doctor?

the smoke is well white and i couldnt notice any distinctive smell as such but twice now when ive turned the choke off she seems to die off when i pull the throttle and not only that its tippin it down in reading at the moment so i dont really want to be out there but as soon as it stops check it out,if it is any of them problems how tricky are they to sort and what would i have to do and get to sort it