I think all of the new ryobi's are the 31's (the old ones with the more square style covering were hit and miss), somewhere on the case should tell the engine displacement. that is a short shaft engine

look for a 11mm carb, if you can't find one with a choke, make the stock choke plate work or something, nothing wrong with a plate style choke, it's less restrictive than a butterfly choke anyway.

the stock connecting rod is fine up til 8000rpm, so prop it for around 7500rpm on the ground for good measure

take the ring off of the piston and place it in the bore, use a feeler gage and find the ring gap, it's most likely around .01 which is too much for getting decent performance, you can get a frank bowman ring for $14 shipped.