Super
(Author unknown; plagiarized from the Web)
The Super Tigre carburetor
has two needle valves for adjusting fuel mixture. The # 1 needle is the
high-speed adjustment needle (on left as viewed from rear of engine, the needle
closest to the fuel inlet nipple). The # 2 needle (on right as viewed from rear
of engine, and close to the throttle linkage attachment) is for slow speed
adjustment. Newer Super Tigre carburetors have gone to a recessed screw in the
barrel for slow speed adjustment. The idle speed adjustment screw is located to
the left of the carburetor throat (as viewed from rear of engine). The screw on
the right of the carburetor throat (as viewed from rear of engine) is the
barrel retaining screw.
Super
To set up this carburetor
you will need a short piece (1 foot) of clean fuel tubing.
First the idle speed adjustment
screw needs to be adjusted so that the throttle barrel is open about the
diameter of a modeling T pin. Later after the idle and mixture has stabilized
and the engine is mounted in the aircraft this setting can be backed off so
that the throttle barrel will close all the way with low throttle and low
throttle trim to kill the engine.
Open the throttle barrel wide
open, then with the length of clean fuel tubing attached to the fuel inlet
nipple, blow through the tubing. Screw the high-speed needle in until you
hear no air escaping. Now open the high-speed needle 2-1/2 turns.
Now with the throttle barrel at
the previously established closed position, gently blow through the
tubing. Adjust the low speed needle in until you can barely hear air
escaping. Now open the low speed needle 1/2 turn from
this position.
Bear in mind if you
change the position of the throttle stop you will have to reset the low speed
needle. Also the setting on the high-speed needle will affect the low speed
transition. I have had the best luck trying to get a reliable idle and good
transition with brand new Super Tigre engines after they are properly broken
in. I have run as much two gallons of fuel through Super Tigre ringed engines
before the idle and transition stabilized to an acceptable level. The breaking
in of a Super Tigre engine is time consuming and if not rushed, will reward you
with an engine that should almost last a lifetime.
With the engine mounted on your
aircraft it is time to start it. Fill the fuel tank and open the carburetor
wide open. With your finger over the carburetor throat (and glow plug driver
NOT CONNECTED) bring the prop up on the compression stroke and slowly turn it
through one revolution. You should see fuel flow into the fuel line and into
the carburetor, flip through about two more revolutions with your finger over
the throat. If when you remove your finger from the carburetor throat and the
fuel in the fuel line flows back into the tank, this could be an indication
that your fuel tank is too low relative to the carburetor’s centerline. Go to
low throttle, high throttle trim on your radio. Connect the glow driver and
with a chicken stick flip the prop through until the engine starts. Some of the
hotter Super Tigre engines that I have had had a propensity to start in
reverse. If this is the case try rotating the prop backwards against
compression and letting it pop back. Usually the engine will start and run in
the proper direction. If the engine starts and will idle fairly well, let it
run for a minute or two to allow the engine to come up to operating
temperature. Advance the throttle slowly to wide open. Listen to the engine and
determine if it's four stroking or two stroking. If it's four stroking screw in
the high-speed needle until the engine transitions to two stroke. Now open the
high-speed needle until the engine just goes into four stroke. Back off the
throttle to idle and have a helper hold the aircraft. With the helper holding
the aircraft advance the throttle to wide open. Have your helper point the nose
of the aircraft to the sky. If the engine speeds up to a stable two stroke, the
high-speed needle is set properly. If the engine is new, I generally open the
high-speed needle about 1/8th turn additional to ensure a rich high end until
it's broken in.
Once the high-speed needle is
set, return the aircraft to the level position and set the throttle to low
throttle/high trim. If the engine is idling let it idle a few seconds then
slowly advance the throttle. If the engine burbles, and it may spit fuel out
the throat, it's too rich. If this is the case, close (clockwise) the low speed
needle about 1/8th turn. Run the engine to full throttle to clear it out then
return to idle for 10 to 20 seconds then slowly advance the throttle. Repeat
the above procedure until you have a smooth throttle transition. If the engine
sags and hesitates with no burbling it means the low speed needle is too lean.
Open (counter clockwise) the low speed needle about 1/8th turn and try it
again. This is the most time consuming part of adjusting any model engine carburetor
so be patient. Once you are satisfied with the idle and transition return the
throttle to wide open and recheck the high speed setting as per the previously
outlined method and make the necessary small changes, then fly.
Note: Do not be tempted to short
cut the break-in, burn at least a gallon of fuel with the high speed set rich.
After break-in is accomplished do not try to adjust to the last few higher
rpm's, as this is the quickest way to turn your Super Tigre engine into a so-so
performer (or worse) rather than a star performer. Also do not use the glow
plug that came with the engine, substitute an OS #8 plug.
Some have reported that the
venturi can be rotated from it's straight down position to a slightly forward
facing position to improve low speed transition. I have never encountered a
problem that made this necessary, but it remains something to consider if all
else does not give satisfactory results.