Saito Fg-90R3

Despite the rapid development of electric motors, which are increasingly transforming into powerful counterparts, internal combustion engines, which closely resemble their full-size prototypes in sound, continue to hold an overwhelming fascination for model enthusiasts. This is especially true for radial engines, which impress with their unmistakable sound.

The FG90 R3 from Saito has been available from aero-naut for some time and is currently one of Saito’s most powerful radial engines. Therefore, we would like to put this engine to the test and write a short report about it here.

According to Saito, the FG 90R3, similar to the FG 60, is also derived from the FA-220 glow engine. Among other things, a gasoline-compatible carburetor was installed, and the cylinders and cylinder heads are machined from a single piece. The crankshaft features dual ball bearings. As with the FG84 R3, large heat sinks are mounted on the housing, which are intended to be positioned in the propeller’s airflow to ensure optimal heat dissipation from the crankcase. The magnetic sensor appears to be of the same type as on the FG60 and is mounted at an angle to the side. The exhaust outlet is routed to the rear, which means the CM6 spark plug sits well protected at an angle. Almost a little too hidden, because when a ring silencer (which must be purchased separately) is mounted, it gets quite tight when attaching and locking the spark plug cap. The carburetor is again located behind the mounting plate, although this time the throttle lever has moved to the left side. However, Saito seems to have learned from the “complaints” about the carburetor on the FG 60 radial engine: this time, there is the option to choke the engine from the outside. When installed, it was more than cumbersome to draw fuel into the engine with both the 60 and the 84.

For the currently most up-to-date model, the FG90 R3 being tested here, Saito has also come up with a practical solution: in the middle of the throttle lever, there is a connection to the internal choke valve, which can be operated using the included “choke stick”. To do this when installed, a 4 mm hole must be provided in the cowl and possibly the front of the motor firewall. So that the carburetor can be primed without a second person holding the choke stick in position, a collar or similar should be installed in the cowl to keep the stick in the required position. After priming, the choke stick can be removed again. Unfortunately, servo-controlled priming is not provided. The main needle valve is located to the top right of the throttle lever, and the idle needle is located in the throttle lever. Choking naturally does not adjust the idle needle, because the fitting for the choke stick is a thread directly on the throttle lever. Therefore, when readjusting the needle, the stick must be unscrewed so that the carburetor adjustment stick can be used.
In addition to the previously mentioned stick for choking, the engine also comes with the carburetor adjustment stick. Due to the wealth of information on the engine structure on the aero-naut website, it is not necessary to explain this again at this point.