Chainsaw Repair

I have a Ryobi Rcs 3540 C.  I am not sure that it has the correct carburettor fitted.  Its a 35cc engine and it has a Zama CIQ H64.  I think it is either the wrong or a faulty carb as I can't get the chainsaw to run properly all the time despite clean it and trying all sorts of adjustments to the L & H screws.  It runs intermittently and makes it a pig to use.

It seems that the CIQ H64 has maybe been replace but I cannot find this out, for certain.  I was wondering if I could maybe use another carb  type or make that I could modify to use via the existing controls & fittings.  Does anyone have any experience of doing this successfully?

I would much appreciate your comments.