Hi Dave,
I'm using the FA-90R3 carb. Lairs had indicated in an earlier reply that both Saito engines use the same carb and I'm sure he is correct as horizon hobby listed the same part number for both engine a while back. You can look on the web for a parts breakdown for both engines and verify part numbers. At the time I just ordered sub assemblies to make up one carb because they were on back order so long. The part number for the throttle barrel assembly is; SAI90R3-87, High speed needle valve; SAI60T85, Carb body assembly; SAI90R3831. All ordered from Horizon and cost about $10 more over ordering the full assembly. The above assemblies come with o-rings and assemble to be a complete carb, no additional parts needed. I worked on my engine some more yesterday and I think my ignition will last at least 30 minutes as I made a better ground by attaching it to the engine case rather than the engine mount. I'm getting a hotter plug now. I'm going to give it a try again this week and hope the engine will run a little longer. I might be buying the McDaniels system? I think Horizon has the full carb back in stock now. I'll let you know how the next run turns out! Be careful, the FG90R3 is the fuel version carb not the glow version you'll need which is FA90R3 engine components.

Ed