RE: RCAero JC Engines & YDA Engines
The engine you have there is one of the ones that got supplied through the JC engines chain.
It will be a WT 645 Carb. Diaphragm kit is a K10 WAT (Or a D10 - one has more "bits" than the other).
If you remove the carb make sure you don't overtighten the mounting bolts when replacing it as it will distort the rubber reed retainer if you do so. A drop of blue loctite on the bolts and gently tighten them is more than enough.
When replacing the diaphragm, use the Tan colored one (Teflon) which is also what should be on it from new
Also make sure the choke is closing properly.