DCRC Club Meeting
Third Friday of each
Month
7:30 PM
Montgomery County
Council building
100 Maryland Ave
Rockville, MD
PROGRAM: Tom Pfarr
RAFFLE: David Garri-
son
Don’t forget the model
shop.
Volume 59, Issue 2
DCRC
NEWSLETTER
DCRC Club Meeting
March, 15 2013
District of Columbia Radio Control Club Montgomery County Maryland AMA Chartered Club 329 Established 1951
Bealeton IMAA 2003
Jim and Joseph McDaniel getting their Cub ready
Volume 59, Issue 2 Page 2
DISTRICT OF COLUMBIA RADIO CONTROL CLUB
Xipp Engine Tuning Method
by: Xipp, Flying Giants
Gas Engine Tuning
Carbs aren't too difficult to
tune up if you know what you're doing.
First of all, you need to know how the
carb works and how the settings inter-
act with each other. About 95% of all the
gas airplanes I've seen at the field are
somewhat out of tune. How can I tell
this? Simple, at some point the engines
"four cycle" in flight. Two Cycle engines
are not supposed to "four cycle" PE-
RIOD. This is caused by a rich mixture
that is forcing the sparkplug to inter-
mittently miss making it sound like a
four stroke. This is not good. HOW-
EVER the good news is; gasoline two
stroke engines are very tolerant of rich
settings (most of the time) and will run
fine. You'll just consume a little more
gasoline than necessary, and create a
little more oil mess on your plane. You
may eventually foul your spark plug as
well. So why do so many people leave
their engines tuned like this? Simple
answer, the engine will start much eas-
ier when it's cold AND there's little or
no warm up time needed prior to flying.
Those are pretty good reasons! But the
fact is... the engine is not running like
it's supposed to.
(1) The low end needle on a Walbro carb
is ALWAYS the one closest to the en-
gine, the high end needle is the closest
one to the intake/choke.
(2) There is no fuel adjustment for idle
fuel, only air feed set by the idle stop or
servo.
(3) Both low end AND high end needles
feed the top end fuel supply.
Let's tune up a Walbro!
Set the low end & high end needles to
about 1 to 1 1/2 turns each. Choke the
carb or prime it, until the carb is wet.
Fire up the engine and let it warm up.
Let's set the top end first since it's the
easier of the two. Go to full throttle.
Adjust the top end needle for peak RPM.
Leave it wide open for about a minute to
see if it changes any. Should the engine
go lean, open the low end needle
slightly, if this doesn't work... you will
have to adjust the needle valve inside
PRESIDENT: Jim McDaniel
V.P. Walt Gallaugher
County Liaison: Jim McDaniel
BOARD OF DIRECTORS
Andy Finizio
Jim Fisher
Walt Gallaugher
David Garrison
Allan Hoffman
Andy Kane
Jim McDaniel
Jose Sanchez
Thomas Pfarr
TREASURER:
Doug Harper
MEMBERSHIP SECRETARY:
Jose Sanchez
20017 Haller Ave
Poolesville, MD 20837
RECORDING SECRETARY:
Doug Harper
SHOW TEAM MANAGER:
Jim McDaniel & Allan Hoffman
NEWSLETTER EDITOR:
Andy Kane
MEETING PROGRAM COORDINATOR:
Walt Gallaugher
OFFICIAL CLUB PHOTOGRAPHER:
Thomas Pfarr
The DC/RC Newsletter is published monthly
by the District of Columbia Radio Control Inc.
Deadline for submitting materials for publica-
tion is the last Friday of each month. Any part
of the newsletter may be reproduced for non-
profit purposes unless otherwise noted. Please
credit the Newsletter and Author if named.
Articles may not reflect the opinion of the club,
but that of the author.
www.dc-rc.org Did you know that any airplane brought in to the
model shop will receive 3 free raffle tickets. Bring in
your models each month for your free tickets, and to
share ideas.
Some reminiscing from Bealeton 2003
Photo by Mike Dooley
GAS ENGINE HOW TO SET YOUR
CARB
PG 2
BOARD MEETING MINUTES PG 3
BUILD YOUR OUR TANK (CONT) PG 4
CLUB MEETING MINUTES PG 5
CLUB MEETING MINUTES PG 6
CALENDAR OF EVENTS PG 7
the carb.( I will explain this later) If the
top end runs OK, then slowly pull the
throttle down until the engine begins to
"four cycle" hold the throttle there. Ad-
just the low end needle until the "four
cycling" stops. Now lower the throttle
more until it "four cycles" again, and
adjust the low end again. Keep doing
this until you reach full idle. Now, from
full idle begin to throttle up until the
engine starts to bog or hesitate. Open up
the top end needle just enough to elimi-
nate the bog or hesitation.
When this is done right, you will be able
to set the throttle in any position and it
won't four cycle, plus you will be able to
transition from idle to full power with-
out any hesitation at all. -Xipp, Flying-
cirkus.com Member
Understanding a Walbro Carb
Ok this is for people who need a little
insight into how a carburetor works in
this case I will be using a Walbro for
example.
Starting from the gas tank, the fuel is
pumped from the fuel tank and enters
the carb through the inlet. The fuel
works its way through the fuel pump
through a little diaphragm pump that's
controlled by 2 one way valves (little
flaps). The fuel then passes through a
needle & seat that is controlled by the
"float" diaphragm. This "float" dia-
phragm manages how much fuel is
available for the idle, low-speed, and
high-speed throttle positions. The "float"
diaphragm opens & closes the needle
through a small lever attached to the
needle. The fuel is then "standing by"
waiting in the float area for a vacuum
signal at the various jets. The lever set-
ting is very critical since it controls the
available fuel to the jets. If the lever is
too low, the engine will run lean, if the
lever is too high, the engine will run
very rich and will likely flood out at idle
The fuel starts its journey through the
pump assembly first...
Then the fuel is regulated by the float
diaphragm that controls the needle &
seat.
All of these parts reside in the float cav-
ity area as well as the fuel ready to be
(Continued on page 3)
DISTRICT OF COLUMBIA RADIO CONTROL CLUB
Volume 59, Issue 2 Page 3
January Board
Meeting Minutes BY DOUG HARPER
The meeting, held at the
home of Andy Finizio, was called to
order by President Jim McDaniel at
6:10 PM. In attendance were Andy
Kane, Allan Hoffman, Jim McDaniel,
Walt Gallaugher, Doug Harper, Jim
Fisher, Dave Garrison, Andy Finizio
and Jose Sanchez.
Committee Reports:
Public Relations & County Liaison:
Jim McDaniel reported that the
County Office Building meeting room
has been retained for another year for
our use. Jim also reported that the
AMA Leader Club Status is in effect
for another year.
Sound & Safety: The Board asked
Walt Gallaugher to come up with a
procedure to create an annual pilot
proficiency assessment for all mem-
bers who use the field. Walt will re-
port back next month with his sug-
gestions on how to do this.
Field Maintenance: Allan Hoffman
reported that the repairs to our signs
have been done.
Flight Instruction/Awards: Jim
Fisher is contemplating a "user fee"
to help offset some of the training
costs in the coming year. He will
work out the details as we get closer
to the training season.
Jim asked for help constructing new
trainers for the coming year. The
Board will help Jim and welcomes
other members who would like to help
as well. Jim also reviewed the list of
IPP instructors for the coming year.
Events: Jim reported that we have
the Soccerplex for indoor flying every
Wednesday from 11:45 to 3:45 from
now to 3/6/13. In addition, we can
use the facility in the month of Febru-
ary up to 6:30PM on Wednesday as
well as on Friday from 9AM to 4PM.
Treasurer: Doug Harper reported
that he wrote five checks over $100 in
the last month. He presented a YTD
Budget report to the Board for their
consideration.
Membership: Jose reported that we
have 102 paid members to date.
Newsletter: Andy Kane. No report.
Web Master: Tom Pfarr. No report.
Old Business: The Board conducted a
lengthy discussion about any prospec-
tive change in our fiscal strategy for
the coming year in lieu of no increase
in dues. After much back and forth,
they decided to stay on the course al-
ready set. Namely, a budget was
passed in late 2012 for the 2013 year
and that budget is still in effect and
will be used to fund Club activities for
the coming year. The Board commit-
ted to try to spend funds prudently
where possible but, in effect, there
will be no change to our budget. Also,
the Board, as well as Club Members,
should look for ways to raise addi-
tional funds where feasible to aug-
ment our dues income. Andy Kane
made a motion to continue with the
current budget for the 2013 year. The
motion was carried unanimously.
New Business: None.
The meeting was adjourned at 9 PM
fed through the jets as needed. The
amount of fuel available in the cavity is
regulated by the lever and its relation-
ship to the float diaphragm. So it's criti-
(Continued from page 2)
cal that the lever be set properly. Within
the cavity, there are distribution holes
that are managed by the low end and
high end needles. Plus the idle circuit,
which is a fixed size.
(Note) All Walbro carbs will run in any
position, but they tune "best" as a side
draft carb. The down draft position
tends to run a little rich at idle, and the
updraft tends to run a little lean at idle.
No big deal though, it's easily tuned
none the less.
This photo depicts one of Walbro's pre-
mier carbs, having a large bore and
equipped with a high speed check valve
and external fuel pump pulse inlet.
Now let's talk about the pulse signal for
the fuel pump.
Your ENGINE will determine which
pulse inlet type you need! If the engine
"carb base" has a hole drilled into the
crankcase you will use the STANDARD
pulse port and the optional (if you have
it) port must be closed off. If there's no
hole drilled, you will find a fitting lo-
cated somewhere on your crankcase.
Use a piece of fuel line to connect the
crankcase fitting to the fitting on the
(Continued on page 7)
Volume 59, Issue 2 Page 4
DISTRICT OF COLUMBIA RADIO CONTROL CLUB
How to Build Your
Own Fuel or Smoke
Tank By Andy Herold
Continued from last month
In the first phase we made
the plug for a custom tank.
Now we will make the
mold. The first thing we
will do is to make a parting board to
hold the plug while making the actual
mold. This board will be where we
create the top and bottom to your
mold and will be where the glue joint
in your tank will be.
You will need two 1/4 inch pieces of
luan plywood about 6 inches larger
than the plug’s dimensions. One will
create a flat edge all the way around
the plug. The other will just act as a
flat base to work on making them one
unit. You will need a piece of Formica
( countertop material ) some Home
Depots have 2 ft X 4 ft pre-cut pieces.
The Formica is not glass smooth and
may have a sandy texture to it. Using
3M spray adhesive or contact cement,
laminate it to one of the pieces of luan
plywood. Next you will cut an opening
in the luan/Formica for the plug. You
want this to be a very close fit, 1/8
inch max. When laying out the cut-
line use masking tape to mark the
lines on. This will prevent the For-
mica from chipping.
Using a hand jig saw and a sharp
fine-toothed blade, cut on the marked
lines. Go slowly to prevent chipping.
You may need to sand the rounded
corners for a perfect fit. You will need
to support the plug firmly in the part-
ing board so that it does not shift dur-
ing the lay-up process. You can use
white foam or blocks of wood like I
have. (See photo #12.) Once you have
the parting board and the plug fitted
to each other, you will need to seal
any gaps between the plug and part-
ing board.
To do this, modeling clay is pushed
into the small gap with a popsicle
stick. Sand one end of the stick square
and a taper to cut the clay after push-
ing it into the gap all the way around
the plug (See photos #13 & #14.) If the
tank is symmetrical and you need to
be able to tell front from back, use a
few small blobs of clay on the flat
mold surface to create humps in the
surface. Now that we have the plug
fitted to the parting board and all the
gaps filled, carefully apply 6 coats of
mold release wax to the plug and
parting board being careful not to
move the plug while applying or re-
moving the wax. Make sure to get wax
on all surfaces including the clay.
While applying the wax and while it
is drying, I cut the fiberglass mat in
preparation for the lay-up process. We
will need 4 layers of fiberglass mat for
each side. Cut the fiberglass mat
making 4 pieces. Two for the flat area
of the parting board one for the plug
the sides the parting board, and one
for the bottom of the plug. Cut each of
the pieces about 1 1/2 inches oversized
for overlap and waste. We will be fray-
ing the edges of the mat so that they
will lay-up into the 90 degree corners
better. The pieces that will be used
on the parting board will only be
frayed on one side. The pieces that
will be making the ends, sides and
bottom or top will be frayed on all
sides.
Now that the fiberglass mat is cut,
using pliers or your fingers pull the
edges of the mat creating the frayed
edge. (See photos #15 & #16.)
Once all the wax has been applied and
buffed off, we can apply 4 very thin
coats of PVA with a normal automo-
tive paint spray gun creating a me-
chanical barrier between the gelcoat
and the plug. These coats of PVA
must be very thin, Use 100 psi air
pressure and adjust the flow rate
down, you should barely be able to see
any of the PVA material coming out of
the spray gun. Allow the PVA to dry
between each coat. Coat the entire
area that was waxed following the
instructions on the can of release
Photo #11
Photo #12
Photo #16
Photo #15
Photo #17
DISTRICT OF COLUMBIA RADIO CONTROL CLUB
Volume 59, Issue 2 Page 5
CLUB MEETING
MINUTES FEBRUARY
2013 BY DOUG HARPER
agent.
We are now ready to apply the orange
polyester tooling gel-coat with the
dump gun. Mix the gelcoat with the
hardener using the correct amount for
the ambient temperature you will be
working in. (Hot temp use less hard-
ener- cool temp more, follow the mfg.
recommendations.) This is a messy
process and should be done outside
due to overspray. Spray the entire
plug and parting board surface mak-
ing sure that you get all corners of the
plug to parting board well coated. You
want to put it on heavy but not to the
point of running. It does not have to
be pretty just well covered. If you get
it too heavy the air pressure will blow
the gel-coat around and cause it to
ripple. Try to avoid this but don’t
panic if it does. (See photo # 17.)
After the gel-coat has cured for about
4-6 hours, it should be hard but still
tacky to the touch. We will be apply-
ing the first two of four layers total.
We are doing this in two steps to
avoid building up heat and pulling the
gel-coat away from the plug. Now
measure out a cup of polyester resin,
(I started with 3oz for this mold ) then
a separate cup of hardener of the
proper amount for the resin and set it
aside. Mix a small amount of the gel-
coat (about 2 oz) with hardener then
add phlox into it to make a peanut
butter consistency. Now spread this
mixture into the corners on the part-
ing board with a tongue depressor,
creating a filet in the corners. Make
sure there are NO AIR POCKETS.
(See photo #18.)
Once that is done, mix your first cup
of polyester resin. Using a 1 inch dis-
posable paintbrush lay the first piece
of mat around the parting board, al-
lowing the frayed edge to overlap up
into the filet you just created. Don’t
worry if the mat overhangs the part-
ing board. Wet this glass completely
out all the way around. Now do the
sides of the plug in the same way al-
lowing the sides to wrap down over
the glass mat that you just wet out
and to wrap up over to the bottom of
the plug. Wet this glass mat out. Then
add the bottom to finish covering all
the gel-coated surface. Once you have
that done, immediately add the sec-
ond layer. You can reverse the order
of lay-up working down to the parting
board. The second layer will soak up
some of the polyester resin from the
first layer. These layers should be
completely wetted but not soaking
wet, (See Photos #19 & #20.)
Let these layers cure overnight.
To be continued next month.~
Photo # 18
Photo #19
Photo # 20 The meeting, held at the
County Office Building, was called to
order by President Jim McDaniel at 7:36
PM. Jim asked for the
introduction of any new
members or guests. Jer-
emy Nelson was present
and intends to join the
Club. He is just getting
into RC. Martin Green is
a new member who in-
tends to fly fixed wing planes. Bruce
Drury is a full scale RV8 pilot. He is
looking at RC as a possible hobby.
Jim again indicated his intention of
minimizing the business content of the
meeting.
Public Relations: Jim announced that
DCRC has qualified as an AMA Gold
Leader Club again this year. We also
have rented the County meeting room
for the coming year.
Events: Jim announced that the indoor
flying has been extended to 5:00 PM for
the remaining Wednesdays of February.
We also have Friday till 4 PM thru the
end of February. The Soccerplex does
withhold the right to take the field back
if a paying customer shows up.
Heritage Day is set for June 29, 2013,
from Noon to 4PM. Opening Day will be
in April, date to be determined.
Training/Community Outreach : Our
first STEM night is April 11 at Orchard
Grove Elementary School followed by
Rockville Science Day on
April 28 at Montgomery
C o m m u n i t y C o l l e g e
(Rockville Campus). Jim
Fisher plans to contact
AMA and Model Airplane
News to get copies of
magazines that we can
distribute to various locations.
Field Maintenance: Allan Hoffman. No
report.
Membership: Jose Sanchez. Member-
ship is open and he solicited all mem-
(Continued on page 6)
Volume 59, Issue 2 Page 6
DISTRICT OF COLUMBIA RADIO CONTROL CLUB
bers to send their renewal. Cards are
on the way.
Safety Coordinator: Walt announced
that AMA has published guidelines for
field sound. He encouraged Club Mem-
bers to read this in the AMA magazine.
Walt plans to have an annual Club
safety review. His checklist included
c h e c k i n g b a t t e r i e s
(including cycling), going
over the fuel system in-
cluding the tank and
clunk, making sure control
services and linkages are
solid, inspecting the prop
and nut, tightening motor
mounts, making sure servo
mounts and connectors are tight, and
finally doing a range check. Frank Ne-
her suggested that the wing attachment
be checked so the wing stays on in
flight. Jim Fisher suggested that those
flying 2.4GHz make sure the transmit-
ter is bound to the correct plane. Andy
Finizio recommended that a thorough
inspection be conducted on the inside of
the fuse to make sure everything is
solid.
Raffle: Jim Fisher and Dave Garrison
presented a BNF Edge 540 QQ indoor
flyer for tonight's raffle. Gus Crosetto
pulled the winning ticket that was held
by Walt Gallaugher. Walt, a member of
the Board, thanked the group for their
resounding approval.
Treasure’s Report: Doug wrote one
check in excess of $100 this month. He
had a copy of the YTD Budget Report for
anyone who cares to see it.
Web Site: Tom Pfarr. All is good.
Newsletter: Andy Kane. No report.
Awards: Award night will be held dur-
ing the April Club Meeting. Jim asked
members to submit names to him of
people who should receive awards.
Flight Training: Jim Fisher announced
that the first day of Training is April 20.
Jim plans to run 20 people through
training this year so that everyone gets
a longer time on the sticks. He also
plans to have separate dates for mem-
bers and IPP folks. There should be as
many as 19 training days this year.
(Continued from page 5) Jim announced that new training mod-
els have been ordered and will be built
by Jose Sanchez. We should also have
some spare parts in case they are
needed. (Modified) Giant Big Stiks will
be used this year and hopefully will
stand up to the use. Jim asked if any
Club members could do vinyl logos and
lettering.
New/Old Business: Hank Jacob sug-
gested last month that DCRC consider
placing an AMA magazine with a note
about DCRC at various places of busi-
ness around the County. Andy Kane
printed label sheets that can be applied
to magazines that members can leave in
various public locations (like Doctor's
offices).
Model Shop: Gus Crosetto presented his
pusher delta Force One kit from Balsa USA.
He received this kit from member Ron Bozi-
netti when he moved to Florida. It weighs
around 4 pounds by using a lighter battery.
He finished it in stars and stripes with a very
attractive scheme. He is using a modified
12X6 prop. He had to work on getting the CG
correct but feels he has achieved that. He
plans to fly it at the next opportunity.
David Harris presented his miniature rubber
powered sea plane based on an Aronca K
design from a kit supplied by Comet. It has a
24" wingspan and Dave built it with both
floats and wheels. He covered it with pre-
colored tissue and produced a very attractive
result. He is working on getting it to fly
longer.
Andy Kane presented his B17 Bomber ARF
from Hobby Lobby. It is very attractively
finished in olive drab with an 63" wingspan
and four electric motors that are all linked
together electrically. It also features operat-
ing flaps and retracts. The left and right
motors counter rotate. It made quite an in-
teresting noise as the four engines revved up.
Andy also talked about his new Quique
Somenzini version of the DX18 radio from
Spektrum. It features some additional pro-
gramming options and comes in a very attrac-
tive black case.
Program: Tonight's program is presented by
Don Gray on the subject of
"weight and balance". Don
referenced Dave Garrison's
very interesting talk last
month on the F106 and de-
cided to present some of the
planes he worked on when he
was in the Air Guard in the
late '60s. These included the F-100 Super
Saber as well as the F-86 Saber, the T-33
Trainer and the F-105 Thunderchief. The
Thunderchief was very high maintenance.
Don feels this is a good time of the year to
think about weight and balance since we are
finishing our winter building projects and
getting ready for the coming flying season.
He listed the effects of weight and balance
which include longer takeoff run, lower rate
and angle of climb, higher cruise speeds( in
sailplanes), increased sink rate and reduced
wind effects ( heavier is better).
Don indicated that wing loading (weight over
area) is much more important than weight
alone in predicting performance. This affects
stall speed as well as other flight perform-
ance parameters. Don then presented data
he has developed on 13 different full-scale
aircraft where he compared actual versus
predicted stall speeds. He found that he
could come quite close to predicting this pa-
rameter.
Don then discussed vertical CG location
(versus longitudinal CG) on roll stability. A
CG above the centerline is a destabilizing
factor and, conversely, a CG below the center-
line stabilizes an airplane. He showed a cou-
ple of examples of each of these.
Don then presented a balance equation which
is used to calculate the CG of a plane by sum-
ming the weights and moments of various
components around a common point (like the
wing leading edge).
Don then moved to the technique he uses to
balance a model airplane. He starts by level-
ing the plane in roll and pitch. He then de-
termines the weight under each landing gear
wheel. He also showed how to determine the
Mean Aerodynamic Chord for a tapered wing.
He uses 25% of MAC as a rule of thumb for
determining CG to start. He also talked
about how to do this for a delta wing.
Don then presented the See-Saw Equation
that he uses to fine tune weight around the
CG. This comes down to making sure a given
weight a certain distance from the CG is bal-
anced by an equal weight times distance on
the other side of the CG. This can be an it-
erative process.
Finally, the CG can be fine tuned by flying
the aircraft and making final adjustments to
the CG. That is a subject for another day.
Don received a resounding round of applause
for his informative talk.
Jim announced that next month's meeting is
March 15. The raffle for next month is a
brand new 120 ABC glow engine.
The meeting adjourned at 9:00 PM.
Volume 59, Issue 2 Page 7
DISTRICT OF COLUMBIA RADIO CONTROL CLUB
Indoor flying at Soccerplex
every Wednesday 11:45 till 3:45 pm through Feb 27
March
15 DCRC Club Meeting Tom Pfarr
17 PGRC Sprinf Auction, Falls Church VA
20 DCRC Board Meeting Tom Pfarr
April
19 DCRC Club Meeting Jim Fisher
24 DCRC Board Meeting Jim Fisher
May
1-5 Top Gun Scale Competition, Lake-land, FL
11-18 Joe Nall Fly IN, Woodruff, SC
17 DCRC Club Meeting David Garri-son
22 DCRC Board Meeting David Garri-son
25-30 First in flight Jet Rally, Wilson NC
June
21 DCRC Club Meeting Allan Hoffman
26 DCRC Board Meeting Allen Hoff-man
July
19 DCRC Club Meeting Allan and Andy K
24 DCRC Board Meeting Allan and Andy K
August
1-4 Summer Afterburner Jet Meet Hamburg, PA
16 DCRC Club Meeting Walt
Gallaugher
16-18 Giant Scale IMAA Hamburg, PA
20 DCRC Board Meeting Walt
Gallaugher
September
6-9 DCRC Bealeton IMAA Flying Cir-cus, VA
20 DCRC Club Meeting Andy Kane Nominations
Calendar of Events 2013
optional pulse inlet. There's no need to
block off the standard port, as it's al-
ready blocked off by the engine mount-
ing.
The carb must get a pulse signal from
the engine! This signal "pushes and
pulls" on the pump diaphragm which
feeds the carb fuel.
Now let's check out the "float needle &
seat" setting.
This is the single most critical setting on
a Walbro carb! Walbro offers a "setting
gauge" to properly set the height of the
lever for your particular carb. If you
don't have one, the setting will be a trial
& error adjustment and a real pain in
the butt since you have to open up the
carb to make the adjustment. For gen-
eral purposes, the lever will be almost
perfectly parallel to the carb base. This
will get you close. If the lever is too high,
your engine will tend to run a little er-
ratic at idle. If the lever is too low, your
idle will be OK but it will tend to run
lean on midrange and high end. It may
also run the float cavity "dry" at full
throttle and die, regardless of your high
speed /low speed needle settings.
The needle valve seat is pressed into the
carb base, and you should not remove
this without having the correct tools and
setting gauges. Do not remove it!
Typical PROBLEMS The engine stalls
when accelerated: POSSIBLE solution:
High end needle way too lean, or low
end needle slightly lean Engine goes
rich in flight : Low end needle too rich,
(Continued from page 3) float diaphragm needle lever slightly too
high
Engine goes lean in flight : High end
needle slightly lean AND low end needle
is rich, float needle lever may be set too
low
Engine runs good, but no idle at all :
There's crap in the idle jets, the carb
will have to be removed and cleaned.
You may also have an air leak at the
base of the carb. The throttle butterfly
could be damaged or worn out carb
leaks fuel when not running : float nee-
dle is bad or has crap stuck in it, or the
float lever setting may be too high, or
the float diaphragm is bad.
My engine four cycles momentarily
when I back off the throttle, then runs
normal : This is perfectly normal for
carbs NOT equipped with a "check
valve" high speed jet. If you do have the
check valve, then your float needle set-
ting is slightly too high, or your float
needle is leaking a little the fuel leaks
back into the gas tank when it isn't run-
ning : Bad fuel pump membrane, or an
air leak in the fuel line at the carb
NOTE 1:
A very common problem with cowled in en-
gines is, the air pressure in flight changes
the "natural" pressure on the float dia-
phragm. This causes the engine to run rich in
flight. There are several possible fixes avail-
able. Most of the time you can simply tune
your engine for flight by trial & error. How-
ever, the easiest fix is to open up the cowling
around the carb area to lower the air pres-
sure. You may also rotate the cover to differ-
ent positions to see if that works. The "BEST"
fix is to solder a piece of brass tubing where
the vent is, and route the vent line to a better
location. I normally route it into the fuse
going through the firewall. It works perfectly
every time! Plus, your ground tune doesn't
change in flight!
NOTE 2
Carbs equipped with the high speed check
valve are greatly superior for flying aerobat-
ics, or flying whereby the throttle will be
used extensively. The check valve prevents
jet dripping when you back off the throttle.
That's all it does...
Straight through (non-check valved) jets
always drip a little fuel while the throttle is
being backed off, and causes a momentary
four stroking of the engine until the jet stabi-
lizes to the new air flow rate. This is com-
pletely normal.~
First Class Mail
March 2013
Andy Kane/Newsletter Editor
305 Natick Court
Silver Spring, MD 20905
E-mail: [email protected]
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