Saito Fg-90R3

Despite the rapid development of electric motors, which are increasingly becoming powerful counterparts, combustion engines, which are very similar in sound to their large prototypes, continue to have 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 the most powerful radial engines from Saito. Therefore, we would like to subject this engine to a test and write a small report about it here.

According to Saito, the FG 90R3, like the FG 60, can be traced back to the glow plug FA-220. Among other things, a gasoline-compatible carburetor was installed and the cylinders and cylinder heads are made from one part. The crankshaft is double ball-bearing mounted. As with the FG84 R3, large heat sinks are mounted on the housing, which are intended to be located in the air flow of the propeller to ensure optimal heat dissipation from the crankcase. The magnetic sensor appears to be of the same type as the FG60 and is mounted at an angle to the side. The exhaust outlet is routed to the rear, so the CM6 spark plug sits at a well-protected angle. Almost a little too hidden, because when a ring silencer is mounted, which must be purchased separately, it becomes quite tight when attaching and locking the spark plug connector. 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 “grumbling” about the carburetor of the FG 60 radial engine: This time there is the possibility to choke the engine from the outside. In the installed state, it was more than cumbersome with the 60 and also with the 84 to suck in fuel with the engine.

With the currently most up-to-date model, the FG90 R3 to be 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”. For this purpose, a 4mm hole must be provided in the hood and possibly the front of the engine mount in the installed state. So that the carburetor can be sucked in even without a second person holding the choke stick in position, a adjusting ring or similar should be installed in the hood so that the stick remains in the necessary position. After sucking in, the choke stick can be removed again. A servo-controlled suction is unfortunately not provided. The main nozzle needle is located at the top right of the throttle lever and the idle needle in the throttle lever. The choking does not change the idle needle, of course, because the screw connection for the choke stick is a thread directly on the throttle lever. Therefore, the stick must be unscrewed when readjusting the needle so that the carburetor adjustment stick can be used.
In addition to the aforementioned 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 it again at this point.