Saito FG-90R3

Despite the rapid development of electric motors, which are increasingly becoming powerful counterparts, internal combustion engines that sound very similar to their full-scale inspirations 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 want 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, can be traced back to the FA-220 glow engine. Among other things, a gasoline-compatible carburetor was installed, and the cylinders and cylinder heads are manufactured as a single piece. The crankshaft has double ball bearings. As with the FG84 R3, large heat sinks are mounted on the housing, which should be located in the propeller’s airflow to ensure optimal heat dissipation from the crankcase. The magnetic sensor appears to be 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 type spark plug is well-protected and angled. It’s almost a bit too hidden, because when a ring muffler is mounted—which must be purchased separately—it gets quite tight when attaching and locking the spark plug connector. The carburetor is again located behind the mounting plate, though this time the throttle lever has moved to the left side. However, Saito seems to have learned from the “grumbling” about the FG 60 radial engine’s carburetor: this time, there is an option to choke the engine from the outside. When installed, it was more than cumbersome to prime the engine with fuel on the 60 and also the 84.

For the current model, the FG90 R3 being tested here, Saito has come up with an equally practical solution: in the center of the throttle lever, there is a connection to the internal choke flap, which can be operated using the included “choke stick.” To do this, a 4mm hole must be provided in the cowl and possibly the engine mount extension when installed. To ensure you can prime the carburetor without a second person holding the choke stick in position, a wheel collar or something similar should be installed in the cowl so that the stick remains in the necessary position. After priming, the choke stick can be removed. Unfortunately, servo-controlled priming is not provided for. The high-speed needle is located at the top right of the throttle lever, and the low-speed needle is arranged within the throttle lever. Choking does not adjust the low-speed needle, of course, because the screw connection for the choke stick is a thread directly on the throttle lever. Therefore, when adjusting the needle, the stick must be unscrewed so that the carburetor adjustment tool can be used.
In addition to the previously mentioned stick for choking, the engine also comes with the carburetor adjustment tool. Due to the wealth of information on the engine’s construction on the aero-naut website, it is not necessary to explain it again at this point.