FUJI-IMVAC BT-34B Operator’s Manual

Operator’s Manual for BT-34B

SPECIFICATIONS

Displacement: 34cc
Horsepower: 3.2hp @ 11,000 rpm
Ignition Style: CDI Automatic

Ignition Timing

RPM: 1200 – 11,000 rpm
Fuel: Gas/2-cycle engine oil
Weight w/Muffl er: 4.1 lb [1.55kg]

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.

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SAFETY TIPS AND WARNINGS

• Always use a balanced spinner and a balanced prop. An unbalanced spinner and prop
combination will cause high levels of vibration and may cause the propeller shaft to break.

• 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 prop on the engine to prevent it from being thrown off
the engine while running.

• Never use a prop that has hit the ground. Even though it may look good from the
outside, it may be cracked on the inside which may cause it 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 “sucked
in” by the propeller. Never start the engine on loose gravel or sand.

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

FJIZ0034 for FJIG0034 V2Entire Contents © Copyright 2009

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

• Make sure the fuel line is well-secured to the engine and to the fuel tank so that it won't
come off in fl ight.

• Do not use silicone fuel line because it will be attacked by the fuel. Use vinyl or neoprene
rubber fuel line.

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

• Never touch the engine after a run. The engine will be hot and it may burn you.

• Before transporting your model, remove all the fuel from the fuel tank and fuel lines.

• Always use high-quality oil intended for 2-stroke engines.

• Use only low-octane, alcohol-free gasoline. The carburetor diaphragm will gradually
deteriorate if you use gasoline with alcohol (ethanol, gasohol, etc.). You will need to
replace the diaphragm in about 80 hours of operation if you use gasoline with alcohol.

• Muffl er 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
305mm [12"] 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 inside the carburetor over an
extended period of time 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 fi lter. Use a fi lter intended to be used with gasoline
engines. Metal fi lters intended for glow engines are too coarse and will not screen out
fi ner particles. Always fi lter your fuel by using an appropriate fi lter before putting it into
the airplane’s fuel tank.

• 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 on a model airplane.

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

• Gasoline is extremely fl ammable. Keep it away from an open fl ame, excessive heat or
sources of sparks. Do not smoke near the engine or the fuel tank.

• This engine was designed for use in a model aircraft. Do not attempt to use it for any
other purpose.

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

BT-34B ATM Engine

42.5mm Propeller Flange with
Propeller Washer
Propeller Bolt
Muffl er with Muffl er Gasket

PARTS LIST

280mm of Gas Tubing
Spark Plug Wrench
4mm Allen Wrench

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AUTOMATIC IGNITION TIMING MODULE

The BT-34B engine ignition system is a combination of an electronic system and a
mechanical system. The working principle for the automatic ignition timing module
is that it gradually advances the ignition timing as the ignition pulses increase with
increasing engine rpm. The mixture is ignited when the piston is near top dead center
for idling and the timing is gradually advanced as the rpm increase.

SPARK PLUG

The recommended spark plug is a Champion RCJ-6Y or 7Y. To avoid improper
operation or possible engine damage, do not use any other type of spark plugs.
The plug gap should be 0.4mm to 0.6mm [0.016" to 0.024"]. If the plug gap is
incorrect, adjust it with a spark plug gapping tool, wash it with gasoline and allow it
to dry completely before you reinstall the plug in the engine.

Note: If you want to check if the spark plug works, remove the spark plug from the
engine, connect it to the coil and make sure the metallic threaded end of the spark
plug touches the engine. Spin the propeller rapidly through top dead center and
check for a spark. This procedure only works in a dark room as there is too much
light outside to see the spark.

The various spark plug manufacturers have much information on their web sites
regarding spark plug performance and health. For more information, check:

http://www.championsparkplugs.com/sparkplug411.asp

PROPELLER

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

The recommended propellers are:

18" x 10" High Performance Wood Prop

18" x 10" or 18" x 12" Carbon Prop

During our tests, our Fuji-Imvac BT-34B turned a Bolly 18" x 12" carbon prop at 7100 rpm
which translates to roughly 30 lb of static thrust.The engine was new with 60 minutes of
breaking in. The test conditions were: Temperature 59°F [15°C], humidity 20%, elevation
at sea level. Performance may vary depending on atmospheric conditions.

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OIL

Fuji-Imvac has developed a special oil to work with their engines. This oil is of
extremely high quality and it has exceptional lubricating properties. This oil can be
mixed with gasoline at much higher ratios than other engine oils which allows the
engine to develop more horsepower and last longer. It is recommended that you
use Fuji-Imvac oil with all your Fuji-Imvac engines. Break-in procedures are slightly
different than those when using standard oils. Please refer to the table below for oil
contents. Fuji-Imvac Oil bottles of different sizes are available from your Fuji-Imvac
distributor or Hobby Shop.

• Break-in (Stage 1): 1 gallon of gasoline with 50:1 (2%) oil content.

• Break-in (Stage 2): 1 gallon of gasoline with 100:1 (1%) oil content.

• Normal running: In un-cowled or well-cooled installations 150:1 (0.65%) oil
content.

• In-cowled or not-so-good cooling installations 100:1 (1%) oil content.

• Do not try to use these engine oil ratios with any other brand of oil other than the
Fuji-Imvac oil.

• Do not use the Fuji-Imvac oil with any other brand of engines.

• If you have been running the engine on other oil and wish to switch to Fuji-Imvac
oil, follow the break-in procedure for Fuji-Imvac oil.

If Fuji-Imvac oil is not available, or if you prefer to use a different brand of oil, use
the standard fuel/oil ratios as shown below. Never experiment with cheap oil or with
obscure brand names. Be certain to select only high-quality oil that is intended for
use in gasoline R/C model airplane engines.

• Break-in: 1 gallon of gasoline with 25:1 (4%) oil content ratio.

• Normal running: 40:1 (2.5%) oil content ratio.

PREPARE THE ENGINE

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 prop shaft on the fl ywheel using three
5 x 22mm SHCS with lock washers and washers. Use
threadlocking compound on the screws.

3. Install the spark plug in the cylinder head and tighten.

4. Test fi t the muffl er and muffl er gasket. Use two 5x 40mm

hex bolts and washers to hold it in place.

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5. Install a kill switch such as the Great Planes Gas Engine Ignition Switch
Harness (GPMG2150). Install the kill switch servo at least 12" [305mm] away
from the engine.

INSTALLING THE FUJI-IMVAC BT-34B ON YOUR AIRPLANE

Note: The Fuji-Imvac BT-34B must be installed on a 12mm [1/2"] lite ply firewall
or on a 9.5mm [3/8"] birch ply firewall. The firewall must be securely glued to the
airplane. Use triangle stock and pin the firewall with hardwood dowels to reinforce
the firewall glue joints. Never install the Fuji-Imvac BT-34B onto a firewall thinner
than specified because it may fail due to the power of the engine.

Note: The length of the engine from the back on the engine mount to the propeller
washer is 143mm [5.6"] when using the stock (40mm [1.57"]) prop fl ange.

1. Use the supplied template (on the back cover of this manual) to drill the engine
mounting bolt holes and the necessary clearance hole on the fi rewall.

2. Install the engine on the fi rewall using
four 6.4 x 32mm or 1/4" x 1-1/4" socket
head cap screws, four 6mm [1/4"] fl at
or lock washers and four 6mm [1/4"]
blind nuts. Use some threadlocking
compound, such as Great Planes®
Pro™ Threadlocker (GPMR6060), on
the screws.

3. Install the fuel tank in the airframe. Use only gasoline-safe fuel lines. One line
should go to the carburetor and the other is to be used as a vent. You can fi ll the
tank by using the carburetor line as fi ll line if you have access to it or install a
third line to be used as fi ll line.

4. Install a manual kill switch and a radio operated kill switch. Install the kill switch
servo at least 305mm [12"] away from the engine.

5. Install the throttle servo at least 305mm [12"] away from the engine. Make sure
that you get the carburetor’s full range of rotation with your servo travel.

6. Cut all necessary clearance and cooling holes in the cowl.

7. Make sure the cowl is secured to the airplane and that the spinner to cowl

clearance is at least 3.2mm [1/8"].

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