Walbro WT-1107 high-performance carburetor. 

This is a modified version of the stock carburetor used for the G320RC engine, and will also work on other Zenoah/CY engine applications.

Carburetor specs: Walbro WT-1107. 15.88mm bore, 13.5mm venturi, independent tunable high and low speed jets.
 
This Carb has been modified so that the metering spring pop off pressure is 18-20lbs instead of the stock 30-35lbs which allows more fuel to be delivered on demand.