I've just bought an XF650 Freewind, and so far, very happy with it

It's basically stock, but have a Huzar exhaust mounted - jetting is not changed for this, and it bogs a little bit, but not too bad. I want to change the main jets, but I can't tell which type/manufacture the carburetors are - so I don't know which jets to order - can you help me out?
And while we're at it, does it make sense to modify the airbox, or anything else? Maybe take the top cover of, and rejet accordingly?