Advise on jetting for PX200 kitted engine


I want to find out what sorts of jets, should I use for the following.
The machine, I have got at the moment is a PX 200, which has had the transfer and ports worked on, as a 28mm carb, a reed valve and kit polini 207cm3.
I will be getting a SIP Performance exhaust, a centered cylinder head, a full circle crankshaft.
Trying the biggest jets and going down to the correct one, can anyone advise on the size of jet to starts with???