FUJI-IMVAC BF-25EI, BF-34EI Operator’s Manual

Operator’s Manual for BF-25EI and BF-34EI EIS 4-Stroke Engines

™

BF-25EI Specifications

Displacement: 24.5cc
Weight: 2.1 kg [4.7 lb]
Bore/Stroke: 24 x 24mm
Peak Horsepower: 1.6hp @ 7,500 rpm
Peak Torque: .14kgfm @ 5,000 rpm
RPM: 1,400 – 9,000 rpm
Fuel: Automotive Unleaded

Gasoline
Ignition Battery: 4.8V, 850mAh NiMH
(battery pack provides

3.5 hrs. operation)

Manufactured by FUJI-IMVAC, Inc.

YOKOHAMA, 235-0005 JAPAN

Worldwide Distributor (except Japan): Hobbico, Inc.

Champaign, IL 61826 USA

www.fuji-imvac.com

Fuji-Imvac is not related to the original Fuji Engines sold by Mecoa.

BF-34EI Specifications

Displacement: 34cc
Weight: 2.6 kg [5.9 lb]
Bore/Stroke: 39 x 28mm
Peak Horsepower: 2.0hp @ 7,500 rpm
Peak Torque: .20kgfm @ 5,000 rpm
RPM: 1,400 – 7,500 rpm
Fuel: Automotive Unleaded

Gasoline
Ignition Battery: 4.8V, 850mAh NiMH
(battery pack provides

3.5 hrs. operation)

SAFETY TIPS AND WARNINGS

Always use a balanced spinner and a balanced propeller. An unbalanced

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spinner and propeller combination will cause high levels of vibration and may

cause damage to the engine and airframe.

• Always use a lightweight spinner on your engine. Lightweight spinners are
considered to be those with a cone wall of 1mm or less. Heavy spinners could
cause the propeller shaft to break.

• Securely tighten the spinner and propeller on the engine to prevent them from
being thrown off of the engine while it’s running.

• Never use a propeller that has hit the ground. Even though it may look good to
a visual inspection, it may still have a crack. This could cause the propeller to
disintegrate while in use. Do not use a nicked, cracked, or split propeller.

• Keep foreign objects away from the propeller. Make sure that nothing can be
drawn into the propeller. Never start the engine on loose gravel or sand. Make
sure there are no loose clothing or jacket strings that could be drawn into the
propeller. Secure your clothing.

• Keep onlookers sway from the running engine, especially small children.

• Do not attempt to stop the engine by throwing anything into the path of the propeller.

• Make sure the fuel tubing is well-secured to the engine and to the fuel tank so
that it cannot come off in flight.

• Do not use silicone fuel tubing because it will be attacked by the fuel. Use fuel
tubing that is suitable for gasoline.

• Always secure the fuel tubing away from the cylinder head. The engine’s heat
can damage the fuel tubing.

• Never touch the engine after it’s been running. The engine will be hot and
could cause burns.

• Remove all fuel from the fuel tank and fuel lines before transporting your model.

• Always use high-quality oil intended for two-cycle engines.

• Use only low octane, alcohol-free gasoline. The carburetor diaphragm will
gradually deteriorate if you use gasoline with alcohol. You will need to replace
the diaphragm in about 80 hours of operation if you use gasoline that contains
alcohol. “Alcohol” includes ethanol in many gasoline blends.

• Muffler pressure to the fuel tank is not required.

• Do not install your throttle servo or kill switch servo inside the engine
compartment. Doing so could cause radio interference. Install all electronic
radio devices at least 12" inches [305mm] away from the engine. The throttle
pushrod should be non-metallic.

• In case the engine is not to be used for more than a month, drain the fuel tank
and remove any fuel from inside the carburetor. Do this by running the engine
at idle until it quits by running out of fuel. Keeping gasoline for an extended
time in the carburetor will damage the diaphragm valve and clog passages
inside the carburetor.

• Because the carburetor is more complicated than those used in glow engines,
keep the fuel clean by using a fuel filter. Use a filter intended to be used with
gasoline engines. Metal filters intended for glow engines are too coarse and
will not screen out finer particles. Always filter your fuel with an appropriate
filter before filling the model’s fuel tank.

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• If you intend to run this engine on an engine stand, or on any other rigid mount,
use rubber mounts. The crankcase and other parts of the engine may crack if
you do not provide some kind of vibration absorption mechanism. A rubber
mount is not necessary if the engine is mounted in a model airplane.

• Do not operate the engine in a closed room or where ventilation is not adequate.

• Gasoline is extremely flammable. Keep it away from an open flame, excessive
heat, or sources of sparks. Do not smoke near the engine, the fuel tank, or the
fuel storage can.

• This engine was deigned for use in model aircraft. To not attempt to us it for
any other purpose.

• Always install a kill switch that can be operated both manually and via the
R/C transmitter.

ELECTRONIC IGNITION MODULE

Your Fuji-Imvac BF-25EI or BF-34EI EIS engine is equipped with an electronic
ignition module. Electronic ignition uses a battery-powered processor to sense the
position of the engine’s crankshaft and then cause a high-energy spark at the
spark plug to fire the engine at the correct moment. The actual firing of the spark
plug will change with the engine’s RPM so that the engine runs its best at all RPM
within its operating range.

ENGINE PREPARATION

1. Check to see that all screws and bolts are tight. Check carefully for any cracks,

broken, or missing parts. Tighten or replace before proceeding.

2. Install the propeller shaft onto the flywheel.

3. Install the spark plug into the cylinder head.

SPARK PLUG

The required spark plug is a Champion NGK-CMR6A. Do not use any other type
of spark plug, or possible engine damage may result. The plug gap should be set
to 0.024" (0.6mm). If the plug gap is incorrect, adjust it with a spark plug gapping
tool, wash it in gasoline, and allow it to dry before it’s reinstalled in the engine.

PROPELLER

Always use a well-balanced, high-quality propeller.

The recommended propellers are:

22 x 10 wood, or 22 x 12 carbon

Other propellers that can be used are

18 x 8, 20 x 6

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Typical operating RPM are:

20 x 6 Mejzlik Carbon Prop:
BF-25F: 1,400 – 6,600 RPM
BF-34F: 1,300 – 7,200 RPM

18 x 8 Bolly Carbon Prop:
BF-25F: 1,400 – 7,300 RPM
BF-34F: 1,300 – 7,800 RPM

Temperature for the above was 15°C, humidity was 20%. Engines were new, with
100 minutes of break-in running.

ENGINE INSTALLATION

Your Fuji-Imvac BF-25EI or BF-34EI engine must be mounted on a 1/2" [12mm]
lite-ply firewall or a 3/8" [9.5mm] aircraft ply firewall. The firewall must be securely­glued to the airplane. Use triangle stock, and pin the firewall with hardwood
dowels to reinforce the firewall glue joints. Never install your engine onto a firewall
thinner than specified because it may fail due to the engine’s power.

1. Use the supplied template (on the back cover of this manual), to drill the engine

mounting bolt holes.

2. Install the engine on the firewall with four 1/4" x 1'1/4" [6.4 x 32mm] socket-head

cap screws, four 1/4" [6.4mm] flat or lock washers, and four 1/4" [6.4mm] blind
nuts. Use threadlocking compound, such as Great Planes® Pro™ Threadlocker™
(GPMR6060) on the screws. The engine MUST be mounted with the cylinder
head up. DO NOT mount the engine with the cylinder head to the side or down

3. Install the fuel tank in the airframe. Use only gasoline-safe fuel lines. With a two

line fuel tank, one line should go to the carburetor, and one line is used as a vent.

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