each of the screws, apply a drop of
oil to prevent thread damage.
• Normal engine maintenance,
such as adjusting the valves or
carburetor, is permissible
without voiding the warranty.
If you have any questions
concerning maintenance
procedures, please contact the
Horizon/Saito Service Center at
877-504-0233. Our technicians
will be happy to advise you on
maintenance issues.
Valve/Tappet Gap
Adjustment
After approximately one hour of
operation, tappet gap adjustment may
be necessary. When you check the
valves, lubricate the moveable parts.
Also make sure the screw is in tight
before making adjustments to valves.
Adjust the valves to a clearance of
.03mm to .10mm (.002 to .004 in)
using the supplied gauge. The valves
must be adjusted with the engine cold
due to thermal expansion.
Note:
Valves must be in the
compression stroke or closed position
as shown in the following figure.
When adjustment is completed, make
sure you tighten the lock nut.
How to Adjust
Remove the plug and the rocker arm
cover and revolve the propeller slowly
in the clockwise direction by hand.
The intake side rocker arm stops, and
by turning it, the piston reaches the
compression top dead center (TDC).
In that position, adjust with the
included gauge and hexagonal
wrench so tappet gap may be set to
almost zero when the engine is in
the compression stroke. If the gauge
can enter (a limit gauge with a 0.1
mm thickness), the clearance is at
maximum and needs adjustment,
adjust between 0.08 and 0.10mm
(0.002 to 0.004 in.) After the gap is
checked, tighten the lock nut securely.
Do not over-tighten.
The tappet gap is the most important
factor in the maintenance of 4-stroke
engines, and operation with an excess
clearance will degrade performance.
In particular, a large gap aggravates
abrasion of the tappet and the cam
and also increases the unusual sound.
Tappet Adjustment
Adjust between
0.03 – 0.10mm (.002" – .004")
Gauge
(0.1mm Max.)
Screw
• Sometimes it is helpful to tighten an
exhaust nut, etc. when hot.
• When finished flying for the
day, be sure to remove fuel from the
carburetor and the fuel tank.
• If the engine will not be
operated for a long period
of time, remove the plug, the rear
cover, the cylinder-head cover, etc.
and clean thoroughly and re-oil.
Then assemble them in the
original condition and place in a
plastic or air- tight container.
Troubleshooting
Guide
If the engine does not start.
• Check and use a new spark plug if
needed.
• Check fuel lines.
• Check for proper mechanical
function by turning the engine over.
• Check that the carburetor is
correctly installed.
Mechanical Faults
If the engine cannot be turned over
easily:
• It is likely that the piston in the
cylinder is seized.
• Visually examine the piston and
crankcase to find the likely cause of
the engine's mechanical problem.
Engine Maintenence
Do not needlessly disassemble your
Saito single cylinder engine.
If you must disassemble your engine,
please refer to the following steps.
• Cylinder screws should be loosened
in a criss-cross pattern.
• Assemble the cam gear lining up
the timing mark at the “6 o’clock”
position. The crankshaft must be
positioned at the “12 o’clock” or
“top dead center” (TDC) position.
Refer to figure below:
• Reassemble the piston, rod, rocker
arm, pins, pushrod, tappet, etc. in
their original positions. Engine
parts are mated after running
the engine and they must be
reassembled as close as possible to
their original position.
• Assemble the engine, reversing
the criss-cross pattern used in the
disassembly. Prior to tightening
V A l V E / T A P P E T g A P A D J U S T M E N T
13
12
T R O U B l E S h O O T I N g g U I D E
Cam (Intake or Exhaust)
Bench Mark
