stated in cubic inches. The O.S. 160FX
name is telling you that it is a 1.6-cu. in.
displacement engine. The cubic capacity
of an engine is the volume in the
cylinder between the piston at bottom
dead center (BDC) and top dead center
(TDC).
Many people refer to engines by cc,
which in this case is cubic centimeters
and does not stand for cubic capacity.
The O.S. 160FX is actually a 26.23cc
engine and may be the optimum size for
a two-cycle, glow fuel-powered engine.
O.S. has the larger BGX, and MARK has
the 2.1, but you run into the law of
diminishing returns on power vs. weight
when you factor in the large, two-cycle
glow-fuel tanks required for a 10-minute
flight.
It is not unusual to see a 32-ounce
tank on a BGX. The O.S. 160FX will
give you 10 to 15 minutes on a 20-ounce
tank at full power—subject to the
propeller and nitro content being used.
This is a two-cycle engine and has
fewer moving and static parts than the
YS four-cycle, yet it will turn similarsized
propellers—depending on the fuel
and the muffler systems. The standard
O.S. muffler and scale “can-type”
mufflers give good sport power.
When the O.S. 160FX is used with a
tuned pipe, you can get a Pattern
airplane to go vertical, do a snap roll,
then open up to full throttle and resume
vertical climb with the same speed used
prior to the snap. A lightweight, carbon
tuned pipe will give an 11-pound Pattern
model unlimited vertical, with a 17 x 13
APC propeller.
The O.S. 160FX is an easy and
straightforward engine to use. After it
has been set up, it needs little attention.
In its standard configuration, it uses
muffler pressure to encourage the fuel to
reach the carburetor.
I have owned and operated more than
20 of these engines and still run them in
my Hangar 9 106-inch Cub and Airborne
Models 80-inch Mustang. I still have a
few in boxes as well.
You can run this ringed engine as it
comes out of the box. After breaking in
February 2012 77
Eric Henderson | ehengineman@The Engine Shop gmail.com
Also included in this column:
• Fixing muffler problems
• Starting the engine
Exploring O.S. engines
The O.S. 160FX—a powerhouse in a small package—is a prime
example of a large, modern, two-cycle glow fuel-powered engine.
Right: Swinging a large propeller mandates that jam nuts and the
main mixture needle are positioned far away from fingers.
INMYOCTOBERcolumn,
I explored
the impressive, but complex, YS 140.
This engine has metamorphosed itself
into many variants, including a pump
instead of a regulator, and even a
computerized ignition version. The latter
was a YS 175 that won the 2011 FAI
F3A World Championship, held at AMA
Headquarters, in Muncie, Indiana.
The O.S. 160FX is a lesscomplicated
engine with similar power.
Although there also is a fuel injection
version of the 160 that uses a computer
module, the basic O.S. 160FX has
changed little since its inception.
The O.S. 160FX is less expensive to
own and run than the equivalent fourcycle
engine. It will operate on the
cheaper 10-15% nitro/methane-based
two-cycle glow fuel. With a standard
muffler, it will turn propellers in the
range of 15 to 18 inches in diameter
with pitches of 6 to 14.
The cubic capacity designation of
two-cycle glow-plug engines is often
02sig3.QXD_00MSTRPG.QXD 12/16/11 1:52 PM Page 77fuel mixture of the 60F will not be consistent enough throughout
the throttle range.
To get the same pressure as a standard muffler, you need the
total muffler gas exit area to at least be equal to that of the stock
muffler. Most “can-type” mufflers that I have seen used on the
O.S. 160FXs are loud and have a large exhaust opening area. You
could block off an entire pipe on some of the canister mufflers,
and the engine would run better. (A tachometer can confirm these
results. Quiet engines can be misleading.)
I have seen field repairs where pilots have crimped the ends of
these pipes to reduce the total size of the exit aperture until the
carburetor could be set. A more professional modification is to
make two aluminum hollow-core plugs on a lathe and pin them in
the ends of the down pipes. Make the total exit area slightly less
than the stock muffler to allow for the fact that there are usually
no baffles in the “cans.”
One tip to pass on is how to better assemble a stock muffler.
The unit is held together with one long bolt. During reassembly,
preheat the bolt with a small butane soldering torch. The heat
expands the length of the bolt. If you quickly assemble and
tighten the bolt, it will be less prone to come loose during
operation. I also use the red, high-temperature, Loctite threadlocking
compound on the threads and on the rims of the mating
exhaust parts. This prevents them from rotating when hot.
78 MODEL AVIATION
a full tank of fuel, you are ready to fly. When you use the
standard muffler it is best to keep the tank as close to the engine
as possible. The big 60F carburetor provides a good mixture
throughout the range, but like many large two-cycle, glow fuelpowered
engines, it does not draw fuel well on its own.
The standard muffler contains a baffle that many users
remove. This may seem to give more power, but it messes with
muffler pressure that goes into the tank. What you see is a good,
top-end run that is plagued by gurgling and hesitation in the midrange
during flight.
Many O.S. 160FX operators accidentally run their 160s too
hot. This leads to problems such as mufflers coming apart, head
bolts loosening, and failed bearings. In extreme cases, the engine
can seize in the cylinder liner or jam the ring in the piston
groove.
One obvious cure is to put the baffle back inside the muffler.
Another solution is to fit an O.S. “F”-type plug. The “F” plug is
designated as a four-cycle glow plug which, by design, runs
hotter. This means that it keeps glowing brighter between
ignition moments. The supplied plug is an A3, which does not
like to get too rich. If you set your transition and mid-range
needle just right, you will end up overheating the cylinder at
sustained full throttle. With an “F” plug, the engine can be set for
full throttle and will recover from a slightly rich mid-range run.
Using after-market mufflers can be tricky. The canister-type
muffler with two down-pipes exacerbates the carburetor-tuning
situation. I have seen Perry carburetors and Kline pump systems
used to remedy the problem.
However, the better solution is to fix the exhaust pressure
problem. If you look closely at a two-cycle muffler, you will see
that the size of the exhaust opening does not match the opening at
the engine exhaust. By size, I mean the total area of the opening.
The opening cannot be too small because it will choke the
engine and reduce the power output. If the opening is too large,
you will lose some of the pressure that bounces the exhaust gases
coming out of the cylinder. This bounce keeps the fresh charge
from spilling out of the cylinder before the piston closes the
exhaust. The muffler provides manageable exhaust pressure that
we can route into the fuel tank air vent. This pressure is low and
varies with the engine’s rpm.
The exhaust pressure supplies glow fuel to the carburetor at
the right time. More rpm uses more fuel and produces more
exhaust pressure at the right time. If this pressure is too weak, the
With a two-cycle engine this big, using an isolation mount will
protect your servos and glue joints.
The O.S. 160FX, side-mounted with an aftermarket Pitts-style
muffler, will fit inside a small cowl.
The heart of all glow fuel-powered, two-cycle engines is the main
bearing. Modelers in the Northeast need to swap in a stainlesssteel
version.
02sig3.QXD_00MSTRPG.QXD 12/16/11 1:53 PM Page 78Starting Tip: The starting technique for a
big, two-cycle engine is different from the
smaller versions. A starter motor is a
common accessory at the field these days.
However, you will need a strong one to
turn over a fuel-loaded and ready-to-fire
O.S. 160FX. Do not worry—there is an
easy way to start these motors without
much 12-volt DC battery power or
physical effort.
With the glow igniter removed, open
the carburetor roughly 25%. Cover the
venture with a thumb or finger and slowly
turn the propeller over four or five times.
Don’t flick the propeller—just keep a grip
on it as you turn over the engine. Move
the throttle back to the idle position, then
light up the plug. One backward flip and
the engine will nearly always burst into
life.
The O.S. 160FX is not immune to ballbearing
rust. Two-cycle, glow-fuel
powered engine bearings can and will
suffer early rust damage from postcombustion
impurities and the byproduct
of moisture from hydrogen molecules
combining with oxygen. An option is toreplace the current problem with a
stainless steel version. There is an article
on the Sport Aviator e-zine about changing
bearings in a big glow engine. The website
address is listed in “Sources.”
Final Tip: Now that we have more
available in-flight telemetry, the
operational world of internal combustion
has changed. You can add a headtemperature
sensor and set your radio
monitoring alarm level to 200° F, and youwill know when to land! MA
Edition: Model Aviation - 2012/02
Page Numbers: 77,78,80
Edition: Model Aviation - 2012/02
Page Numbers: 77,78,80
stated in cubic inches. The O.S. 160FX
name is telling you that it is a 1.6-cu. in.
displacement engine. The cubic capacity
of an engine is the volume in the
cylinder between the piston at bottom
dead center (BDC) and top dead center
(TDC).
Many people refer to engines by cc,
which in this case is cubic centimeters
and does not stand for cubic capacity.
The O.S. 160FX is actually a 26.23cc
engine and may be the optimum size for
a two-cycle, glow fuel-powered engine.
O.S. has the larger BGX, and MARK has
the 2.1, but you run into the law of
diminishing returns on power vs. weight
when you factor in the large, two-cycle
glow-fuel tanks required for a 10-minute
flight.
It is not unusual to see a 32-ounce
tank on a BGX. The O.S. 160FX will
give you 10 to 15 minutes on a 20-ounce
tank at full power—subject to the
propeller and nitro content being used.
This is a two-cycle engine and has
fewer moving and static parts than the
YS four-cycle, yet it will turn similarsized
propellers—depending on the fuel
and the muffler systems. The standard
O.S. muffler and scale “can-type”
mufflers give good sport power.
When the O.S. 160FX is used with a
tuned pipe, you can get a Pattern
airplane to go vertical, do a snap roll,
then open up to full throttle and resume
vertical climb with the same speed used
prior to the snap. A lightweight, carbon
tuned pipe will give an 11-pound Pattern
model unlimited vertical, with a 17 x 13
APC propeller.
The O.S. 160FX is an easy and
straightforward engine to use. After it
has been set up, it needs little attention.
In its standard configuration, it uses
muffler pressure to encourage the fuel to
reach the carburetor.
I have owned and operated more than
20 of these engines and still run them in
my Hangar 9 106-inch Cub and Airborne
Models 80-inch Mustang. I still have a
few in boxes as well.
You can run this ringed engine as it
comes out of the box. After breaking in
February 2012 77
Eric Henderson | ehengineman@The Engine Shop gmail.com
Also included in this column:
• Fixing muffler problems
• Starting the engine
Exploring O.S. engines
The O.S. 160FX—a powerhouse in a small package—is a prime
example of a large, modern, two-cycle glow fuel-powered engine.
Right: Swinging a large propeller mandates that jam nuts and the
main mixture needle are positioned far away from fingers.
INMYOCTOBERcolumn,
I explored
the impressive, but complex, YS 140.
This engine has metamorphosed itself
into many variants, including a pump
instead of a regulator, and even a
computerized ignition version. The latter
was a YS 175 that won the 2011 FAI
F3A World Championship, held at AMA
Headquarters, in Muncie, Indiana.
The O.S. 160FX is a lesscomplicated
engine with similar power.
Although there also is a fuel injection
version of the 160 that uses a computer
module, the basic O.S. 160FX has
changed little since its inception.
The O.S. 160FX is less expensive to
own and run than the equivalent fourcycle
engine. It will operate on the
cheaper 10-15% nitro/methane-based
two-cycle glow fuel. With a standard
muffler, it will turn propellers in the
range of 15 to 18 inches in diameter
with pitches of 6 to 14.
The cubic capacity designation of
two-cycle glow-plug engines is often
02sig3.QXD_00MSTRPG.QXD 12/16/11 1:52 PM Page 77fuel mixture of the 60F will not be consistent enough throughout
the throttle range.
To get the same pressure as a standard muffler, you need the
total muffler gas exit area to at least be equal to that of the stock
muffler. Most “can-type” mufflers that I have seen used on the
O.S. 160FXs are loud and have a large exhaust opening area. You
could block off an entire pipe on some of the canister mufflers,
and the engine would run better. (A tachometer can confirm these
results. Quiet engines can be misleading.)
I have seen field repairs where pilots have crimped the ends of
these pipes to reduce the total size of the exit aperture until the
carburetor could be set. A more professional modification is to
make two aluminum hollow-core plugs on a lathe and pin them in
the ends of the down pipes. Make the total exit area slightly less
than the stock muffler to allow for the fact that there are usually
no baffles in the “cans.”
One tip to pass on is how to better assemble a stock muffler.
The unit is held together with one long bolt. During reassembly,
preheat the bolt with a small butane soldering torch. The heat
expands the length of the bolt. If you quickly assemble and
tighten the bolt, it will be less prone to come loose during
operation. I also use the red, high-temperature, Loctite threadlocking
compound on the threads and on the rims of the mating
exhaust parts. This prevents them from rotating when hot.
78 MODEL AVIATION
a full tank of fuel, you are ready to fly. When you use the
standard muffler it is best to keep the tank as close to the engine
as possible. The big 60F carburetor provides a good mixture
throughout the range, but like many large two-cycle, glow fuelpowered
engines, it does not draw fuel well on its own.
The standard muffler contains a baffle that many users
remove. This may seem to give more power, but it messes with
muffler pressure that goes into the tank. What you see is a good,
top-end run that is plagued by gurgling and hesitation in the midrange
during flight.
Many O.S. 160FX operators accidentally run their 160s too
hot. This leads to problems such as mufflers coming apart, head
bolts loosening, and failed bearings. In extreme cases, the engine
can seize in the cylinder liner or jam the ring in the piston
groove.
One obvious cure is to put the baffle back inside the muffler.
Another solution is to fit an O.S. “F”-type plug. The “F” plug is
designated as a four-cycle glow plug which, by design, runs
hotter. This means that it keeps glowing brighter between
ignition moments. The supplied plug is an A3, which does not
like to get too rich. If you set your transition and mid-range
needle just right, you will end up overheating the cylinder at
sustained full throttle. With an “F” plug, the engine can be set for
full throttle and will recover from a slightly rich mid-range run.
Using after-market mufflers can be tricky. The canister-type
muffler with two down-pipes exacerbates the carburetor-tuning
situation. I have seen Perry carburetors and Kline pump systems
used to remedy the problem.
However, the better solution is to fix the exhaust pressure
problem. If you look closely at a two-cycle muffler, you will see
that the size of the exhaust opening does not match the opening at
the engine exhaust. By size, I mean the total area of the opening.
The opening cannot be too small because it will choke the
engine and reduce the power output. If the opening is too large,
you will lose some of the pressure that bounces the exhaust gases
coming out of the cylinder. This bounce keeps the fresh charge
from spilling out of the cylinder before the piston closes the
exhaust. The muffler provides manageable exhaust pressure that
we can route into the fuel tank air vent. This pressure is low and
varies with the engine’s rpm.
The exhaust pressure supplies glow fuel to the carburetor at
the right time. More rpm uses more fuel and produces more
exhaust pressure at the right time. If this pressure is too weak, the
With a two-cycle engine this big, using an isolation mount will
protect your servos and glue joints.
The O.S. 160FX, side-mounted with an aftermarket Pitts-style
muffler, will fit inside a small cowl.
The heart of all glow fuel-powered, two-cycle engines is the main
bearing. Modelers in the Northeast need to swap in a stainlesssteel
version.
02sig3.QXD_00MSTRPG.QXD 12/16/11 1:53 PM Page 78Starting Tip: The starting technique for a
big, two-cycle engine is different from the
smaller versions. A starter motor is a
common accessory at the field these days.
However, you will need a strong one to
turn over a fuel-loaded and ready-to-fire
O.S. 160FX. Do not worry—there is an
easy way to start these motors without
much 12-volt DC battery power or
physical effort.
With the glow igniter removed, open
the carburetor roughly 25%. Cover the
venture with a thumb or finger and slowly
turn the propeller over four or five times.
Don’t flick the propeller—just keep a grip
on it as you turn over the engine. Move
the throttle back to the idle position, then
light up the plug. One backward flip and
the engine will nearly always burst into
life.
The O.S. 160FX is not immune to ballbearing
rust. Two-cycle, glow-fuel
powered engine bearings can and will
suffer early rust damage from postcombustion
impurities and the byproduct
of moisture from hydrogen molecules
combining with oxygen. An option is toreplace the current problem with a
stainless steel version. There is an article
on the Sport Aviator e-zine about changing
bearings in a big glow engine. The website
address is listed in “Sources.”
Final Tip: Now that we have more
available in-flight telemetry, the
operational world of internal combustion
has changed. You can add a headtemperature
sensor and set your radio
monitoring alarm level to 200° F, and youwill know when to land! MA
Edition: Model Aviation - 2012/02
Page Numbers: 77,78,80
stated in cubic inches. The O.S. 160FX
name is telling you that it is a 1.6-cu. in.
displacement engine. The cubic capacity
of an engine is the volume in the
cylinder between the piston at bottom
dead center (BDC) and top dead center
(TDC).
Many people refer to engines by cc,
which in this case is cubic centimeters
and does not stand for cubic capacity.
The O.S. 160FX is actually a 26.23cc
engine and may be the optimum size for
a two-cycle, glow fuel-powered engine.
O.S. has the larger BGX, and MARK has
the 2.1, but you run into the law of
diminishing returns on power vs. weight
when you factor in the large, two-cycle
glow-fuel tanks required for a 10-minute
flight.
It is not unusual to see a 32-ounce
tank on a BGX. The O.S. 160FX will
give you 10 to 15 minutes on a 20-ounce
tank at full power—subject to the
propeller and nitro content being used.
This is a two-cycle engine and has
fewer moving and static parts than the
YS four-cycle, yet it will turn similarsized
propellers—depending on the fuel
and the muffler systems. The standard
O.S. muffler and scale “can-type”
mufflers give good sport power.
When the O.S. 160FX is used with a
tuned pipe, you can get a Pattern
airplane to go vertical, do a snap roll,
then open up to full throttle and resume
vertical climb with the same speed used
prior to the snap. A lightweight, carbon
tuned pipe will give an 11-pound Pattern
model unlimited vertical, with a 17 x 13
APC propeller.
The O.S. 160FX is an easy and
straightforward engine to use. After it
has been set up, it needs little attention.
In its standard configuration, it uses
muffler pressure to encourage the fuel to
reach the carburetor.
I have owned and operated more than
20 of these engines and still run them in
my Hangar 9 106-inch Cub and Airborne
Models 80-inch Mustang. I still have a
few in boxes as well.
You can run this ringed engine as it
comes out of the box. After breaking in
February 2012 77
Eric Henderson | ehengineman@The Engine Shop gmail.com
Also included in this column:
• Fixing muffler problems
• Starting the engine
Exploring O.S. engines
The O.S. 160FX—a powerhouse in a small package—is a prime
example of a large, modern, two-cycle glow fuel-powered engine.
Right: Swinging a large propeller mandates that jam nuts and the
main mixture needle are positioned far away from fingers.
INMYOCTOBERcolumn,
I explored
the impressive, but complex, YS 140.
This engine has metamorphosed itself
into many variants, including a pump
instead of a regulator, and even a
computerized ignition version. The latter
was a YS 175 that won the 2011 FAI
F3A World Championship, held at AMA
Headquarters, in Muncie, Indiana.
The O.S. 160FX is a lesscomplicated
engine with similar power.
Although there also is a fuel injection
version of the 160 that uses a computer
module, the basic O.S. 160FX has
changed little since its inception.
The O.S. 160FX is less expensive to
own and run than the equivalent fourcycle
engine. It will operate on the
cheaper 10-15% nitro/methane-based
two-cycle glow fuel. With a standard
muffler, it will turn propellers in the
range of 15 to 18 inches in diameter
with pitches of 6 to 14.
The cubic capacity designation of
two-cycle glow-plug engines is often
02sig3.QXD_00MSTRPG.QXD 12/16/11 1:52 PM Page 77fuel mixture of the 60F will not be consistent enough throughout
the throttle range.
To get the same pressure as a standard muffler, you need the
total muffler gas exit area to at least be equal to that of the stock
muffler. Most “can-type” mufflers that I have seen used on the
O.S. 160FXs are loud and have a large exhaust opening area. You
could block off an entire pipe on some of the canister mufflers,
and the engine would run better. (A tachometer can confirm these
results. Quiet engines can be misleading.)
I have seen field repairs where pilots have crimped the ends of
these pipes to reduce the total size of the exit aperture until the
carburetor could be set. A more professional modification is to
make two aluminum hollow-core plugs on a lathe and pin them in
the ends of the down pipes. Make the total exit area slightly less
than the stock muffler to allow for the fact that there are usually
no baffles in the “cans.”
One tip to pass on is how to better assemble a stock muffler.
The unit is held together with one long bolt. During reassembly,
preheat the bolt with a small butane soldering torch. The heat
expands the length of the bolt. If you quickly assemble and
tighten the bolt, it will be less prone to come loose during
operation. I also use the red, high-temperature, Loctite threadlocking
compound on the threads and on the rims of the mating
exhaust parts. This prevents them from rotating when hot.
78 MODEL AVIATION
a full tank of fuel, you are ready to fly. When you use the
standard muffler it is best to keep the tank as close to the engine
as possible. The big 60F carburetor provides a good mixture
throughout the range, but like many large two-cycle, glow fuelpowered
engines, it does not draw fuel well on its own.
The standard muffler contains a baffle that many users
remove. This may seem to give more power, but it messes with
muffler pressure that goes into the tank. What you see is a good,
top-end run that is plagued by gurgling and hesitation in the midrange
during flight.
Many O.S. 160FX operators accidentally run their 160s too
hot. This leads to problems such as mufflers coming apart, head
bolts loosening, and failed bearings. In extreme cases, the engine
can seize in the cylinder liner or jam the ring in the piston
groove.
One obvious cure is to put the baffle back inside the muffler.
Another solution is to fit an O.S. “F”-type plug. The “F” plug is
designated as a four-cycle glow plug which, by design, runs
hotter. This means that it keeps glowing brighter between
ignition moments. The supplied plug is an A3, which does not
like to get too rich. If you set your transition and mid-range
needle just right, you will end up overheating the cylinder at
sustained full throttle. With an “F” plug, the engine can be set for
full throttle and will recover from a slightly rich mid-range run.
Using after-market mufflers can be tricky. The canister-type
muffler with two down-pipes exacerbates the carburetor-tuning
situation. I have seen Perry carburetors and Kline pump systems
used to remedy the problem.
However, the better solution is to fix the exhaust pressure
problem. If you look closely at a two-cycle muffler, you will see
that the size of the exhaust opening does not match the opening at
the engine exhaust. By size, I mean the total area of the opening.
The opening cannot be too small because it will choke the
engine and reduce the power output. If the opening is too large,
you will lose some of the pressure that bounces the exhaust gases
coming out of the cylinder. This bounce keeps the fresh charge
from spilling out of the cylinder before the piston closes the
exhaust. The muffler provides manageable exhaust pressure that
we can route into the fuel tank air vent. This pressure is low and
varies with the engine’s rpm.
The exhaust pressure supplies glow fuel to the carburetor at
the right time. More rpm uses more fuel and produces more
exhaust pressure at the right time. If this pressure is too weak, the
With a two-cycle engine this big, using an isolation mount will
protect your servos and glue joints.
The O.S. 160FX, side-mounted with an aftermarket Pitts-style
muffler, will fit inside a small cowl.
The heart of all glow fuel-powered, two-cycle engines is the main
bearing. Modelers in the Northeast need to swap in a stainlesssteel
version.
02sig3.QXD_00MSTRPG.QXD 12/16/11 1:53 PM Page 78Starting Tip: The starting technique for a
big, two-cycle engine is different from the
smaller versions. A starter motor is a
common accessory at the field these days.
However, you will need a strong one to
turn over a fuel-loaded and ready-to-fire
O.S. 160FX. Do not worry—there is an
easy way to start these motors without
much 12-volt DC battery power or
physical effort.
With the glow igniter removed, open
the carburetor roughly 25%. Cover the
venture with a thumb or finger and slowly
turn the propeller over four or five times.
Don’t flick the propeller—just keep a grip
on it as you turn over the engine. Move
the throttle back to the idle position, then
light up the plug. One backward flip and
the engine will nearly always burst into
life.
The O.S. 160FX is not immune to ballbearing
rust. Two-cycle, glow-fuel
powered engine bearings can and will
suffer early rust damage from postcombustion
impurities and the byproduct
of moisture from hydrogen molecules
combining with oxygen. An option is toreplace the current problem with a
stainless steel version. There is an article
on the Sport Aviator e-zine about changing
bearings in a big glow engine. The website
address is listed in “Sources.”
Final Tip: Now that we have more
available in-flight telemetry, the
operational world of internal combustion
has changed. You can add a headtemperature
sensor and set your radio
monitoring alarm level to 200° F, and youwill know when to land! MA
