MY MENTION OF
Enya engines in a
recent column
brought a quick
reply from David
Pawlowski of
Midland, Michigan.
He informed me
that Enyas are
readily available
from their Japanese
manufacturer: Enya
Direct—and with
amazingly fast
delivery. I checked
this out—and began
a lengthy and
highly educational
e-mail
correspondence
with Ken Enya.
One thing I was
especially curious
about was Enya’s
four-stroke diesel.
That’s because
several of the four-stroke model engines I’ve tested and reported
on had remarkably snappy compression. At those times I thought,
“I wonder whether anyone has ever made a diesel version of one
of these.”
It turns out that Enya has. And Ken sent me one to tell you
about. It’s a .41 and is made with Enya’s typical high-quality and
ingenious design.
That engine is based on the company’s glow 41-4C four-stroke
and uses most of the same parts. Its head even has a threaded hole
for a glow plug, but in the diesel version this is filled with a plug
machined from solid metal. It looks like a glow plug, though.
When I opened the 41-4CD box, I received quite a surprise.
The engine is sold only partly assembled, with many of its small
parts supplied in individual plastic envelopes.
I asked Ken about that, and he told me that he believed that
anyone who bought one of his four-stroke diesels would most
likely be a model engine enthusiast—someone who would enjoy
seeing the guts of this unusual little power plant before putting it
to use.
Assembly and operating instructions that came with the 41-
4CD turned out to be skimpy and imperfectly translated into
English. However, I have seven decades worth of experience with
model engines, and I had no real trouble putting the Enya
together. It helped that a full set of assembly tools comes with the
power plant.
When preparing the 41-4CD, it’s first necessary to remove the
valve rocker assembly. That is attached with a single long screw
and comes off as a complete unit that needs no readjustment when
it’s reattached.
Then I pulled out the pushrods and put a few drops of castor oil
into each of the cam follower holes to lubricate the cams and
gears. A drop of oil onto each rocker pivot seemed like a good
idea too.
Loosening the four head screws came next. It’s unnecessary to
remove the head itself. I did so anyway, because I wanted to see
the combustion-chamber setup. The head needs loosened only
enough to allow the pushrod tubes to be inserted.
August 2010 77
Joe Wagner The Engine Shop | [email protected]
Also included in this column:
• Glow lighter fix
Enya’s diesel four-stroke
Enya’s unique 41-4CD four-stroke diesel.
What looks like a glow plug at the front
of its head is a solid-metal dummy. Of
course, no glow heat is required.
The 41-4CD comes partly put together. Using the various small
parts and tools included, the final assembly is up to the user.
Use Joe’s tips.
Installing the pushrod cover tubes requires removing the rocker
assembly and head. An extra head gasket is supplied for possible
use in hot climates. Joe needed it.
08sig3x.QXD_00MSTRPG.QXD 6/25/10 9:30 AM Page 77
78 MODEL AVIATION
After the tubes are in place, the engine
can be reassembled. Drop the pushrods
into their tubes and put the “top end” back
together.
Tighten all five of the head retaining
bolts—working progressively to seat the
head evenly—as hard as you can without
permanently bending the Allen wrench.
Then add the valve cover.
I found it best to remove the carburetor
before reinstalling the intake tube. That
way it’s easy to get the tube aligned
exactly, thus ensuring that no leakage
occurs at either end. Once the intake tube
is properly lined up in both the carburetor
and the head, reattach the carburetor and
add the muffler assembly.
Extra head gaskets that come with the
41-4CD are needed for hot-weather
operation. The two .0045-inch-thick
gaskets that came installed in my engine
turned out to be all right to provide the
proper compression for easy starting and
smooth running at approximately 70°.
However, when I tried running the
diesel at 88°, sure signs of overheating
showed up: black oil in the exhaust. I took
the top end apart again and installed one
extra gasket. That fixed the overheating
problem nicely.
I judge the correct compression setting
for all of my diesels by the color of their
exhaust oil. I do my best to keep that
light—preferably no darker than iced tea.
Black diesel exhaust oil indicates that
the mixture has begun firing well before
the piston reaches top dead center (TDC).
That means excessive heat, loss of power,
and extra strain on
the wristpin and
connecting rod.
Reducing the
compression cures
all those things and
results in
improved,
smoother running
and more useful
power.
And on the
topic of
compression,
model diesels
aren’t true diesels,
because they lack
fuel injection at the
top of the piston
stroke. Model
“diesel” engines
are more accurately
called
“compression
ignition” types.
Instead of their
fuel-oil-air mixture
being ignited by a
spark or a glowing
coil of platinum
wire, the heat generated by high
compression at the top of the piston’s
stroke causes the ether in the fuel to
combust. That ignites the kerosene, which
makes up 40% of the fuel mixture for
model diesels and provides most of their
power output. Ether content of model
diesel fuel is close to 35% and castor oil is
close to 25%.
Nearly all model diesels feature
adjustable compression. It permits using
high compression while starting and then
reducing compression as the engine
warms up.
That feature is what makes model
diesels so flexible. Most of them can
happily spin any size propeller that will fit
on the shaft. An .03 diesel can turn a 10 x
4. Believe it or don’t.
However, the Enya 41-4CD doesn’t
have adjustable compression. It’s similar
to the first American-made model diesels:
the 1947 Drone .29 and Mite .09. I bought
one of each in February 1947.
They ran fine while the cold
Pennsylvania weather lasted, but by
summer they had become balky and
rough-running. Hot weather made them
fire prematurely once they warmed up.
However, that doesn’t seem to be a
serious problem with the Enya 41-4CD.
Its efficient four-stroke operation and
extensive cylinder and head fins keep its
operating temperature reasonably
constant.
Enya recommends hand-starting for the
41-4CD. Electric starting isn’t entirely
safe for any model diesel, because high
compression makes “hydraulic lock” a
distinct possibility.
The 41-4CD’s piston comes so close to
the top of the combustion chamber at
TDC, the piston’s crown had to have two
semicircular “pockets” machined into it to
provide clearance for the valves. Only a
little liquid fuel in that space would be
enough to stop the piston before it reached
TDC and cause a bent rod or worse during
electric-starting attempts.
Enya recommends propellers from 12
to 14 inches in diameter and 5 to 8 inches
in pitch for the 41-4CD. I chose an APC
13 x 6 to begin with. It’s heavy enough for
good flywheel action—helpful for a diesel
and essential for a four-stroker.
Instructions call for finger choking
before starting, but I’ve found that
awkward to do in upright four-strokes.
Instead, I block off the muffler exhaust
outlet with a fingertip. Flipping the
propeller with the exhaust sealed pushes
pulses of muffler pressure to the tank to
force fuel into the carburetor. As soon as
the engine fires, I take my finger off of the
muffler port and continue flipping
vigorously until the engine starts.
That happened quickly with the 41-
4CD. I left the mixture rich at first, with
clouds of white smoke pouring out of the
exhaust. I wanted to maximize internal
lubrication for the initial few minutes,
because when I first put a propeller on it
and turned it over, the engine felt almost as
snugly fitted as a glow ABC (aluminumbrass-
chrome).
After 40 minutes of running time at
various rpm, the 41-4CD still feels
somewhat snug. However, it has gained
200 rpm at the top end (7600 vs. 7400 at
first) and reduced its reliable idling speed
from 2600 when new to 1900 now.
Two “standard diesel cautions” apply to
Enya’s 41-4CD. First, never flood it!
That’s the main mistake that novice
The Enya 41-4CD purrs on the test stand. It hand-starts easily and
runs quietly. A half-hour to an hour of break-in time is needed for
best idling peformance.
Tower Hobbies’ ProGlo Starter features a
replaceable Ni-Cd battery. Regular
cleaning assures optimal operation. The
optional metered cap is well worth its
extra cost.
08sig3x.QXD_00MSTRPG.QXD 6/25/10 9:31 AM Page 78
dieseleers commit. Flooding prevents
starting. And it’s hard to crank a flooded
diesel dry. That’s because a diesel burns
substantially less fuel than a glow
engine—at least one-third less. I flooded
the 41-4CD once and suffered the
consequences.
Second, never idly flip a diesel’s
propeller. It can start!
I like Enya’s four-stroker. It’s ruggedly
made, easy to start and adjust, and runs as
smoothly as any four-stroke engine I’ve
ever handled. Its performance on the APC
13 x 6 surprised me; that’s a big propeller
for a .41.
Yet maybe I shouldn’t have been
surprised. As I’ve mentioned, model
diesels are renowned for their ability to
swing big propellers. Later, when I tried
an APC 12 x 6 on the 41-4CD, it
performed even better.
I’ve been using Ni-Cd-powered glow plug
lighters for decades. And I always hated it
when the battery finally gave out and I had
to scrap the entire unit when there was
nothing wrong with it except for the dead
battery.
Tower Hobbies’ ProGlo Starter is
different. Its sub-C battery is as easy to
replace as one in a flashlight.
However, a couple months ago I
noticed that my ProGlo wasn’t working as
well as usual. It took a long time to
recharge too, yet tests proved that the Ni-
Cd itself was okay. What happened?
I took the thing completely apart and
found the problem. In time, engine oil had
sneaked its way into the interior of the unit
and formed a thin, high-resistance film
between the electrical contacts.
The cure was obvious: clean everything
with grease-dissolving detergent. Then, as
an extra precaution before putting things
back together, I lightly sanded all
contacting surfaces, including the ends of
the Ni-Cd. That fixed the problem.
My ProGlo has the optional metered
top. This is far from a precision meter, yet
it makes a good diagnostic tool.
For one thing, it instantly detects a
blown plug. For another, it lets you know
when its Ni-Cd needs recharging. The time
I’ve saved by using my metered ProGlo
has made it well worth its extra $10. MA
Sources:
Enya Direct
www.enya-engine.com
Tower Hobbies
(800) 637-6050
www.towerhobbies.com
Edition: Model Aviation - 2010/08
Page Numbers: 77,78,79
Edition: Model Aviation - 2010/08
Page Numbers: 77,78,79
MY MENTION OF
Enya engines in a
recent column
brought a quick
reply from David
Pawlowski of
Midland, Michigan.
He informed me
that Enyas are
readily available
from their Japanese
manufacturer: Enya
Direct—and with
amazingly fast
delivery. I checked
this out—and began
a lengthy and
highly educational
e-mail
correspondence
with Ken Enya.
One thing I was
especially curious
about was Enya’s
four-stroke diesel.
That’s because
several of the four-stroke model engines I’ve tested and reported
on had remarkably snappy compression. At those times I thought,
“I wonder whether anyone has ever made a diesel version of one
of these.”
It turns out that Enya has. And Ken sent me one to tell you
about. It’s a .41 and is made with Enya’s typical high-quality and
ingenious design.
That engine is based on the company’s glow 41-4C four-stroke
and uses most of the same parts. Its head even has a threaded hole
for a glow plug, but in the diesel version this is filled with a plug
machined from solid metal. It looks like a glow plug, though.
When I opened the 41-4CD box, I received quite a surprise.
The engine is sold only partly assembled, with many of its small
parts supplied in individual plastic envelopes.
I asked Ken about that, and he told me that he believed that
anyone who bought one of his four-stroke diesels would most
likely be a model engine enthusiast—someone who would enjoy
seeing the guts of this unusual little power plant before putting it
to use.
Assembly and operating instructions that came with the 41-
4CD turned out to be skimpy and imperfectly translated into
English. However, I have seven decades worth of experience with
model engines, and I had no real trouble putting the Enya
together. It helped that a full set of assembly tools comes with the
power plant.
When preparing the 41-4CD, it’s first necessary to remove the
valve rocker assembly. That is attached with a single long screw
and comes off as a complete unit that needs no readjustment when
it’s reattached.
Then I pulled out the pushrods and put a few drops of castor oil
into each of the cam follower holes to lubricate the cams and
gears. A drop of oil onto each rocker pivot seemed like a good
idea too.
Loosening the four head screws came next. It’s unnecessary to
remove the head itself. I did so anyway, because I wanted to see
the combustion-chamber setup. The head needs loosened only
enough to allow the pushrod tubes to be inserted.
August 2010 77
Joe Wagner The Engine Shop | [email protected]
Also included in this column:
• Glow lighter fix
Enya’s diesel four-stroke
Enya’s unique 41-4CD four-stroke diesel.
What looks like a glow plug at the front
of its head is a solid-metal dummy. Of
course, no glow heat is required.
The 41-4CD comes partly put together. Using the various small
parts and tools included, the final assembly is up to the user.
Use Joe’s tips.
Installing the pushrod cover tubes requires removing the rocker
assembly and head. An extra head gasket is supplied for possible
use in hot climates. Joe needed it.
08sig3x.QXD_00MSTRPG.QXD 6/25/10 9:30 AM Page 77
78 MODEL AVIATION
After the tubes are in place, the engine
can be reassembled. Drop the pushrods
into their tubes and put the “top end” back
together.
Tighten all five of the head retaining
bolts—working progressively to seat the
head evenly—as hard as you can without
permanently bending the Allen wrench.
Then add the valve cover.
I found it best to remove the carburetor
before reinstalling the intake tube. That
way it’s easy to get the tube aligned
exactly, thus ensuring that no leakage
occurs at either end. Once the intake tube
is properly lined up in both the carburetor
and the head, reattach the carburetor and
add the muffler assembly.
Extra head gaskets that come with the
41-4CD are needed for hot-weather
operation. The two .0045-inch-thick
gaskets that came installed in my engine
turned out to be all right to provide the
proper compression for easy starting and
smooth running at approximately 70°.
However, when I tried running the
diesel at 88°, sure signs of overheating
showed up: black oil in the exhaust. I took
the top end apart again and installed one
extra gasket. That fixed the overheating
problem nicely.
I judge the correct compression setting
for all of my diesels by the color of their
exhaust oil. I do my best to keep that
light—preferably no darker than iced tea.
Black diesel exhaust oil indicates that
the mixture has begun firing well before
the piston reaches top dead center (TDC).
That means excessive heat, loss of power,
and extra strain on
the wristpin and
connecting rod.
Reducing the
compression cures
all those things and
results in
improved,
smoother running
and more useful
power.
And on the
topic of
compression,
model diesels
aren’t true diesels,
because they lack
fuel injection at the
top of the piston
stroke. Model
“diesel” engines
are more accurately
called
“compression
ignition” types.
Instead of their
fuel-oil-air mixture
being ignited by a
spark or a glowing
coil of platinum
wire, the heat generated by high
compression at the top of the piston’s
stroke causes the ether in the fuel to
combust. That ignites the kerosene, which
makes up 40% of the fuel mixture for
model diesels and provides most of their
power output. Ether content of model
diesel fuel is close to 35% and castor oil is
close to 25%.
Nearly all model diesels feature
adjustable compression. It permits using
high compression while starting and then
reducing compression as the engine
warms up.
That feature is what makes model
diesels so flexible. Most of them can
happily spin any size propeller that will fit
on the shaft. An .03 diesel can turn a 10 x
4. Believe it or don’t.
However, the Enya 41-4CD doesn’t
have adjustable compression. It’s similar
to the first American-made model diesels:
the 1947 Drone .29 and Mite .09. I bought
one of each in February 1947.
They ran fine while the cold
Pennsylvania weather lasted, but by
summer they had become balky and
rough-running. Hot weather made them
fire prematurely once they warmed up.
However, that doesn’t seem to be a
serious problem with the Enya 41-4CD.
Its efficient four-stroke operation and
extensive cylinder and head fins keep its
operating temperature reasonably
constant.
Enya recommends hand-starting for the
41-4CD. Electric starting isn’t entirely
safe for any model diesel, because high
compression makes “hydraulic lock” a
distinct possibility.
The 41-4CD’s piston comes so close to
the top of the combustion chamber at
TDC, the piston’s crown had to have two
semicircular “pockets” machined into it to
provide clearance for the valves. Only a
little liquid fuel in that space would be
enough to stop the piston before it reached
TDC and cause a bent rod or worse during
electric-starting attempts.
Enya recommends propellers from 12
to 14 inches in diameter and 5 to 8 inches
in pitch for the 41-4CD. I chose an APC
13 x 6 to begin with. It’s heavy enough for
good flywheel action—helpful for a diesel
and essential for a four-stroker.
Instructions call for finger choking
before starting, but I’ve found that
awkward to do in upright four-strokes.
Instead, I block off the muffler exhaust
outlet with a fingertip. Flipping the
propeller with the exhaust sealed pushes
pulses of muffler pressure to the tank to
force fuel into the carburetor. As soon as
the engine fires, I take my finger off of the
muffler port and continue flipping
vigorously until the engine starts.
That happened quickly with the 41-
4CD. I left the mixture rich at first, with
clouds of white smoke pouring out of the
exhaust. I wanted to maximize internal
lubrication for the initial few minutes,
because when I first put a propeller on it
and turned it over, the engine felt almost as
snugly fitted as a glow ABC (aluminumbrass-
chrome).
After 40 minutes of running time at
various rpm, the 41-4CD still feels
somewhat snug. However, it has gained
200 rpm at the top end (7600 vs. 7400 at
first) and reduced its reliable idling speed
from 2600 when new to 1900 now.
Two “standard diesel cautions” apply to
Enya’s 41-4CD. First, never flood it!
That’s the main mistake that novice
The Enya 41-4CD purrs on the test stand. It hand-starts easily and
runs quietly. A half-hour to an hour of break-in time is needed for
best idling peformance.
Tower Hobbies’ ProGlo Starter features a
replaceable Ni-Cd battery. Regular
cleaning assures optimal operation. The
optional metered cap is well worth its
extra cost.
08sig3x.QXD_00MSTRPG.QXD 6/25/10 9:31 AM Page 78
dieseleers commit. Flooding prevents
starting. And it’s hard to crank a flooded
diesel dry. That’s because a diesel burns
substantially less fuel than a glow
engine—at least one-third less. I flooded
the 41-4CD once and suffered the
consequences.
Second, never idly flip a diesel’s
propeller. It can start!
I like Enya’s four-stroker. It’s ruggedly
made, easy to start and adjust, and runs as
smoothly as any four-stroke engine I’ve
ever handled. Its performance on the APC
13 x 6 surprised me; that’s a big propeller
for a .41.
Yet maybe I shouldn’t have been
surprised. As I’ve mentioned, model
diesels are renowned for their ability to
swing big propellers. Later, when I tried
an APC 12 x 6 on the 41-4CD, it
performed even better.
I’ve been using Ni-Cd-powered glow plug
lighters for decades. And I always hated it
when the battery finally gave out and I had
to scrap the entire unit when there was
nothing wrong with it except for the dead
battery.
Tower Hobbies’ ProGlo Starter is
different. Its sub-C battery is as easy to
replace as one in a flashlight.
However, a couple months ago I
noticed that my ProGlo wasn’t working as
well as usual. It took a long time to
recharge too, yet tests proved that the Ni-
Cd itself was okay. What happened?
I took the thing completely apart and
found the problem. In time, engine oil had
sneaked its way into the interior of the unit
and formed a thin, high-resistance film
between the electrical contacts.
The cure was obvious: clean everything
with grease-dissolving detergent. Then, as
an extra precaution before putting things
back together, I lightly sanded all
contacting surfaces, including the ends of
the Ni-Cd. That fixed the problem.
My ProGlo has the optional metered
top. This is far from a precision meter, yet
it makes a good diagnostic tool.
For one thing, it instantly detects a
blown plug. For another, it lets you know
when its Ni-Cd needs recharging. The time
I’ve saved by using my metered ProGlo
has made it well worth its extra $10. MA
Sources:
Enya Direct
www.enya-engine.com
Tower Hobbies
(800) 637-6050
www.towerhobbies.com
Edition: Model Aviation - 2010/08
Page Numbers: 77,78,79
MY MENTION OF
Enya engines in a
recent column
brought a quick
reply from David
Pawlowski of
Midland, Michigan.
He informed me
that Enyas are
readily available
from their Japanese
manufacturer: Enya
Direct—and with
amazingly fast
delivery. I checked
this out—and began
a lengthy and
highly educational
e-mail
correspondence
with Ken Enya.
One thing I was
especially curious
about was Enya’s
four-stroke diesel.
That’s because
several of the four-stroke model engines I’ve tested and reported
on had remarkably snappy compression. At those times I thought,
“I wonder whether anyone has ever made a diesel version of one
of these.”
It turns out that Enya has. And Ken sent me one to tell you
about. It’s a .41 and is made with Enya’s typical high-quality and
ingenious design.
That engine is based on the company’s glow 41-4C four-stroke
and uses most of the same parts. Its head even has a threaded hole
for a glow plug, but in the diesel version this is filled with a plug
machined from solid metal. It looks like a glow plug, though.
When I opened the 41-4CD box, I received quite a surprise.
The engine is sold only partly assembled, with many of its small
parts supplied in individual plastic envelopes.
I asked Ken about that, and he told me that he believed that
anyone who bought one of his four-stroke diesels would most
likely be a model engine enthusiast—someone who would enjoy
seeing the guts of this unusual little power plant before putting it
to use.
Assembly and operating instructions that came with the 41-
4CD turned out to be skimpy and imperfectly translated into
English. However, I have seven decades worth of experience with
model engines, and I had no real trouble putting the Enya
together. It helped that a full set of assembly tools comes with the
power plant.
When preparing the 41-4CD, it’s first necessary to remove the
valve rocker assembly. That is attached with a single long screw
and comes off as a complete unit that needs no readjustment when
it’s reattached.
Then I pulled out the pushrods and put a few drops of castor oil
into each of the cam follower holes to lubricate the cams and
gears. A drop of oil onto each rocker pivot seemed like a good
idea too.
Loosening the four head screws came next. It’s unnecessary to
remove the head itself. I did so anyway, because I wanted to see
the combustion-chamber setup. The head needs loosened only
enough to allow the pushrod tubes to be inserted.
August 2010 77
Joe Wagner The Engine Shop | [email protected]
Also included in this column:
• Glow lighter fix
Enya’s diesel four-stroke
Enya’s unique 41-4CD four-stroke diesel.
What looks like a glow plug at the front
of its head is a solid-metal dummy. Of
course, no glow heat is required.
The 41-4CD comes partly put together. Using the various small
parts and tools included, the final assembly is up to the user.
Use Joe’s tips.
Installing the pushrod cover tubes requires removing the rocker
assembly and head. An extra head gasket is supplied for possible
use in hot climates. Joe needed it.
08sig3x.QXD_00MSTRPG.QXD 6/25/10 9:30 AM Page 77
78 MODEL AVIATION
After the tubes are in place, the engine
can be reassembled. Drop the pushrods
into their tubes and put the “top end” back
together.
Tighten all five of the head retaining
bolts—working progressively to seat the
head evenly—as hard as you can without
permanently bending the Allen wrench.
Then add the valve cover.
I found it best to remove the carburetor
before reinstalling the intake tube. That
way it’s easy to get the tube aligned
exactly, thus ensuring that no leakage
occurs at either end. Once the intake tube
is properly lined up in both the carburetor
and the head, reattach the carburetor and
add the muffler assembly.
Extra head gaskets that come with the
41-4CD are needed for hot-weather
operation. The two .0045-inch-thick
gaskets that came installed in my engine
turned out to be all right to provide the
proper compression for easy starting and
smooth running at approximately 70°.
However, when I tried running the
diesel at 88°, sure signs of overheating
showed up: black oil in the exhaust. I took
the top end apart again and installed one
extra gasket. That fixed the overheating
problem nicely.
I judge the correct compression setting
for all of my diesels by the color of their
exhaust oil. I do my best to keep that
light—preferably no darker than iced tea.
Black diesel exhaust oil indicates that
the mixture has begun firing well before
the piston reaches top dead center (TDC).
That means excessive heat, loss of power,
and extra strain on
the wristpin and
connecting rod.
Reducing the
compression cures
all those things and
results in
improved,
smoother running
and more useful
power.
And on the
topic of
compression,
model diesels
aren’t true diesels,
because they lack
fuel injection at the
top of the piston
stroke. Model
“diesel” engines
are more accurately
called
“compression
ignition” types.
Instead of their
fuel-oil-air mixture
being ignited by a
spark or a glowing
coil of platinum
wire, the heat generated by high
compression at the top of the piston’s
stroke causes the ether in the fuel to
combust. That ignites the kerosene, which
makes up 40% of the fuel mixture for
model diesels and provides most of their
power output. Ether content of model
diesel fuel is close to 35% and castor oil is
close to 25%.
Nearly all model diesels feature
adjustable compression. It permits using
high compression while starting and then
reducing compression as the engine
warms up.
That feature is what makes model
diesels so flexible. Most of them can
happily spin any size propeller that will fit
on the shaft. An .03 diesel can turn a 10 x
4. Believe it or don’t.
However, the Enya 41-4CD doesn’t
have adjustable compression. It’s similar
to the first American-made model diesels:
the 1947 Drone .29 and Mite .09. I bought
one of each in February 1947.
They ran fine while the cold
Pennsylvania weather lasted, but by
summer they had become balky and
rough-running. Hot weather made them
fire prematurely once they warmed up.
However, that doesn’t seem to be a
serious problem with the Enya 41-4CD.
Its efficient four-stroke operation and
extensive cylinder and head fins keep its
operating temperature reasonably
constant.
Enya recommends hand-starting for the
41-4CD. Electric starting isn’t entirely
safe for any model diesel, because high
compression makes “hydraulic lock” a
distinct possibility.
The 41-4CD’s piston comes so close to
the top of the combustion chamber at
TDC, the piston’s crown had to have two
semicircular “pockets” machined into it to
provide clearance for the valves. Only a
little liquid fuel in that space would be
enough to stop the piston before it reached
TDC and cause a bent rod or worse during
electric-starting attempts.
Enya recommends propellers from 12
to 14 inches in diameter and 5 to 8 inches
in pitch for the 41-4CD. I chose an APC
13 x 6 to begin with. It’s heavy enough for
good flywheel action—helpful for a diesel
and essential for a four-stroker.
Instructions call for finger choking
before starting, but I’ve found that
awkward to do in upright four-strokes.
Instead, I block off the muffler exhaust
outlet with a fingertip. Flipping the
propeller with the exhaust sealed pushes
pulses of muffler pressure to the tank to
force fuel into the carburetor. As soon as
the engine fires, I take my finger off of the
muffler port and continue flipping
vigorously until the engine starts.
That happened quickly with the 41-
4CD. I left the mixture rich at first, with
clouds of white smoke pouring out of the
exhaust. I wanted to maximize internal
lubrication for the initial few minutes,
because when I first put a propeller on it
and turned it over, the engine felt almost as
snugly fitted as a glow ABC (aluminumbrass-
chrome).
After 40 minutes of running time at
various rpm, the 41-4CD still feels
somewhat snug. However, it has gained
200 rpm at the top end (7600 vs. 7400 at
first) and reduced its reliable idling speed
from 2600 when new to 1900 now.
Two “standard diesel cautions” apply to
Enya’s 41-4CD. First, never flood it!
That’s the main mistake that novice
The Enya 41-4CD purrs on the test stand. It hand-starts easily and
runs quietly. A half-hour to an hour of break-in time is needed for
best idling peformance.
Tower Hobbies’ ProGlo Starter features a
replaceable Ni-Cd battery. Regular
cleaning assures optimal operation. The
optional metered cap is well worth its
extra cost.
08sig3x.QXD_00MSTRPG.QXD 6/25/10 9:31 AM Page 78
dieseleers commit. Flooding prevents
starting. And it’s hard to crank a flooded
diesel dry. That’s because a diesel burns
substantially less fuel than a glow
engine—at least one-third less. I flooded
the 41-4CD once and suffered the
consequences.
Second, never idly flip a diesel’s
propeller. It can start!
I like Enya’s four-stroker. It’s ruggedly
made, easy to start and adjust, and runs as
smoothly as any four-stroke engine I’ve
ever handled. Its performance on the APC
13 x 6 surprised me; that’s a big propeller
for a .41.
Yet maybe I shouldn’t have been
surprised. As I’ve mentioned, model
diesels are renowned for their ability to
swing big propellers. Later, when I tried
an APC 12 x 6 on the 41-4CD, it
performed even better.
I’ve been using Ni-Cd-powered glow plug
lighters for decades. And I always hated it
when the battery finally gave out and I had
to scrap the entire unit when there was
nothing wrong with it except for the dead
battery.
Tower Hobbies’ ProGlo Starter is
different. Its sub-C battery is as easy to
replace as one in a flashlight.
However, a couple months ago I
noticed that my ProGlo wasn’t working as
well as usual. It took a long time to
recharge too, yet tests proved that the Ni-
Cd itself was okay. What happened?
I took the thing completely apart and
found the problem. In time, engine oil had
sneaked its way into the interior of the unit
and formed a thin, high-resistance film
between the electrical contacts.
The cure was obvious: clean everything
with grease-dissolving detergent. Then, as
an extra precaution before putting things
back together, I lightly sanded all
contacting surfaces, including the ends of
the Ni-Cd. That fixed the problem.
My ProGlo has the optional metered
top. This is far from a precision meter, yet
it makes a good diagnostic tool.
For one thing, it instantly detects a
blown plug. For another, it lets you know
when its Ni-Cd needs recharging. The time
I’ve saved by using my metered ProGlo
has made it well worth its extra $10. MA
Sources:
Enya Direct
www.enya-engine.com
Tower Hobbies
(800) 637-6050
www.towerhobbies.com
