O.S. Engines 91HZ-R - Manual (Page 9)

16
INSTALLATION OF THE ENGINE
The under-surfaces of all O.S. engine beam
mounting lugs are precision machined flat and
exactyly parallel to the engine's horizontal axis. It is
essential that the engine mounts in the model are
also accurately made and aligned. If they are not,
they will cause stress and distortion within the engine
itself, probably resulting in loss of performance and
internal damage.
The recommended screws for securing the engine to
the engine mounts in the model are 4mm or 4-40
steel Allen type. It is also advisable to use lock
washers or LOCTITE to prevent nuts from loosening.
Front view
CORRECT
Side view
Top surfaces are in the same plane.
Re-align the surfaces as necessary
INCORRECT
Top surfaces are not
in the same plane. Top surfaces are not in the
same plane.
Engine does not rest firmly.
Make sure that only the under-
surfaces of the engine’s mounting
lugs are in contact with the engine
mount.
17
INSTALLATION OF THE STANDARD ACCESSORIES
INSTALLING THE GLOWPLUG
Install washer on glowplug
and insert carefully into
Heatsink-head, making sure
that it is not cross-threaded
before tightening firmly.
Glow plug
Washer
The knurled heads of the two needle valves (High-
Speed and Medium Speed) are provided with
diagonal slots for use with a screwdriver.
Alternatively, formore positive location via an Allen
hexagonal key, these heads also have M2.6 internal
threads, into which M2.6x5mm Allen cap-head screw
may be installed. To avoid risk of damage to the fuel
passages when tightening these screws, remove the
needle valves from the carburetor and use 'Loctite'
thread-lock compound to secure the screw.
HEX KEY NEEDLE ADJUSTMENT
Needle Adjusting screw
ABOUT THE HEAD GASKET
The engine is installed with a 0.1mm thick head
gasket at the factory. When a 15% nitro fuel is used,
run the engine as it is. When a 30% nitro fuel is used,
replace with a 0.2mm thick gasket supplied or add
0.2mm thick gasket for easier tuning.