Chapter 4
Brief Description of Design &
Maintenance
Engine
The motorcycle is equipped with a twin-cylinder four-stroke
carburetor-type air-cooled engine. Opposed arrangement of
cylinders in the horizontal plane is the outstanding feature of the
motorcycle design which ensures proper cooling and balancing of
the crank gear. The engine valves are arranged in the cylinder
heads.
In summer, carefully observe the heating condition of the engine,
power transmission units and the running gear mechanisms.
Under normal heating conditions of the engine, the temperature of
the cylinder heads should not be over 356°F-428°F/180°C-220°C.
The
crank gear
incorporates the cylinders, the pistons with piston
rings and pins, the connecting rods with bearings (Figs. 4 & 5) and
the crankshaft with the flywheel.
The
engine cylinders
(Fig. 5, #8) are identical in design and
interchangeable. A gasket is fitted between the cylinder and the
crankcase.
When mounting the left-hand cylinder, see that the
holes in the gasket are in line with those in the crankcase
through which oil is fed for lubrication of the
above-mentioned cylinder and oil is drained from the valve
box.
Piston, piston rings and piston pins.
The engine piston has
three milled grooves for fitting the piston rings. When the piston is
installed into the cylinder, the clearance in the lock should be
within 0.25 - 0.50 mm. The piston is coupled to the connecting rod
by means of a floating piston pin with circlips.
Crankshaft and connecting rod.
The engine crankshaft is made
up of two crank portions arranged in one plane at 180°. It has two
journals with main journals and counterweights, the cheek and two
crankpins (Fig. 5, #26) which serve as connecting rod journals.
Crankcase.
The crankcase accommodates the cylinders, the
timing gear and auxiliary mechanisms. It also serves as an oil
container. Oil Filter (Fig. 4, #22) mounted in the timing gear cover
is stopped with plug (Fig. 4, #24) incorporating a bypass valve.
