Evolution Engines 91NX - Manual (Page 9)

EN
9
After each flying session:
1. Fully drain the fuel from the tank.
2. Start the engine and run it until the fuel is
completely run out of the engine.
3. Try starting the engine three more times or
until it will no longer fire. This gets all the
fuel out of the engine.
Now add several drops (about 10) of after-run
oil (EVOX1001 Evolution Engine’s Blue Block
After Run Oil) into the carburetor and the
engine should turn over for a few seconds
with the starter. This will prevent rust and
corrosion.
Why would fuel go “bad”?
The largest portion of the fuel is methanol
(alcohol). Methanol is hygroscopic; it attracts
moisture. This can cause your fuel to be
contaminated with water, which will cause
poor engine performance. Additionally, the
UV rays in sunlight will eventually break down
the nitromethane if the fuel jug is stored in
sunlight for long periods of time.
How can you tell when your fuel has gone
“bad”?
The first indication will generally be the in-
ability to start the engine at previously run
needle-valve settings. Another clue might be
that the engine has very poor idle runs, but
bogs down tremendously during run up and/
or will not attain the same rpms that you are
used to.
How do I keep my fuel fresh?
If you have the opportunity, look for someone
at a flying field on a sunny day who has a
jug of fuel that is only 1/4 full. What you may
notice is that there are droplets attached to
the top and sides of the container. This is the
moisture in the air that is condensing inside
the jug because of the greenhouse effect in
a semi-translucent plastic jug. This will also
occur within a metal fuel can if the sun warms
the contents.
You can combat the effects of the moisture
in the air by squeezing all the extra air from
your fuel container at the end of the day or
transferring your fuel into smaller containers.
Many pilots will invest in 1/2 gallon or quart-
size containers and only bring that amount of
Maintenance
Low-Speed SetRight Needle Valves
The design of the SetRight needle valve
system is such that, during normal operating
conditions, the typical user will find that the
range of adjustment allowed by the system is
more than adequate for most situations. As a
matter of fact, we intended this to be used as
a tool to identify operating problems. If you
find that the range of adjustment allowed by
the SetRight needle is inadequate after your
initial period of running, then a problem in
your engine system has occurred. This might
be a bad glow plug, dirty or old fuel, an air
leak in the fuel system somewhere or any
number of other reasons. Do not make any
permanent adjustment range changes to the
SetRight needle system if it was once working
correctly for you and now does not.
Investigate other problems first.
However, occasionally due to atmospheric,
altitudinal or fuel conditions, you may find
that the range of adjustment built into the
SetRight needle valve system is inadequate
for your needs. These conditions are rare and
easy to fix. Low-Speed SetRight Needle Valve Correction
Should the low-speed SetRight needle valve
need to be adjusted outside the factory-
established parameters, follow these steps:
A. Loosen the setscrew found on the ring of
the SetRight assembly to which the
adjustment bar is attached.
B. Rotate the needle valve itself (small
slot-headed screw inside the blue ring of
the SetRight assembly) clockwise to lean
the mixture or counterclockwise to richen
the mixture as desired.
C. Retighten the setscrew on the ring of the
SetRight assembly and you have
re-established a new range of motion.