The FS-81 is the second engine in the new generation of 4-stroke FsSeries engines. Since the major dimensions are the same, including the mounting dimensions, the new FS-81 can easily replace an existing FS-70SII with little reworking. With an increase in power due to the displacement increase in conjunction with light weight, scale type aircraft can realize more scale like flight and sport models an increase in performance. The distinctive shape of the engine and silencer symbolize this new generation of 4-stroke FS Series engines

The new crankcase design and blue anodized rocker cover are symbols of this new generation FS Series 4-stroke.
Mounting bolt pattern, distance between crankcase and propeller and throttle lever position are the same as those of the FS-70SII
The latest available materials are utilized for the internal parts such as high silicon aluminum for the piston.

A unique feature of the FS Series is the new and innovative blow-by oil treatment system which eliminates the crankcase vent. Instead of ejecting the blow-by oil out of the crankcase by means of the breather nipple, the oil is now sucked from the crankcase via the pushrod tube to the rocker chamber and injected into the cylinder via a hole leading to the intake valve.

The new silencer can be adjusted both in and out as well as rotated to meet individual cowling requirements.

The silencer exhaust outlet can be rotated 360 degrees.

@A bold new design and sharp cooling fins are unique to the FS Series. The silencer can be adjusted both in and out as well as rotated to match individual cowling requirements. Internal parts employ the latest available materials and are machined with the latest technology. Models designed to be powered by 2-stroke .40-.60 size engines would be suitable for the FS-81 engine. Ample power is available for those heavier, scale type models.

The new 60RA carburetor is equipped with an extended intake tube to restrain any reverse flow, or blow back, of the air/fuel mixture which, in turn, contributes to lower fuel consumption. The carburetor can also be rotated 180 degrees for needle-valve and actuating arm connection. The carburetor has an intake bore of 7mm, the same as the FS-70SII. The silencer utilizes two piece construction with an internal baffle plate for a more quiet and pleasant sound. A threaded connecting manifold enables adjustment of the distance between the engine and silencer as well as the silencer angle

FS - 81

Displacement 13..26cc
Bore 27.7mm
Stroke 22.0mm
Output 1.3ps/11,000r.p.m.
Practical r.p.m.Range  2,200`12,000 r.p.m
Weight 610g (including 54g of silencer and manifold)