Evolution Engines 91NX - Manual (Page 8)

EN
8
The low-speed needle has a limiter that
prevents over-adjustment. If your engine
starts from the above procedure, but won’t
reliably continue to run with the glow driver
removed, follow the steps below.
High-Speed Needle Adjustment
With the engine running, advance the throttle
to full throttle while a helper securely holds
your airplane. Carefully pinch and release the
fuel line to temporarily restrict the fuel flow.
High-Speed Needle Adjustment
CAUTION: Do not reach over the
propeller while the engine is running.
Correct: If the high-speed needle adjustment
is correct, the engine will increase rpm slightly
(about 300 rpm) and then resume normal
operation.
Too Rich: If the engine increases a lot (1,000
rpm or greater), the high-speed needle is too
rich and must be leaned or turned clockwise.
Too Lean: If the engine doesn’t increase rpm
and simply dies, the high-speed needle is
lean and must be richened or turned counter-
clockwise.
Low-Speed Needle Adjustment
The low-speed or idle needle valve, included
with the SetRight
™ assembly, is preadjusted
at the factory for best performance at close to
sea level conditions. It may be necessary to
fine-tune the low-speed adjustment using the
following procedure:
1. Start the engine and let it warm up, prior
to attempting any adjustments. Make sure
that the high-speed adjustment process is
complete before attempting to adjust the
low-speed needle valve.
Low-Speed Needle Adjustment
The low-speed needle adjustment range is
limited, preventing adjustment beyond the
practical range.
2. Close the throttle slowly. You will adjust
the low-speed needle setting by rotating
the SetRight adjustment bar clockwise to
lean the engine and counterclockwise to
richen the engine.
CAUTION: Do not attempt to adjust
the low-speed needle valve while the
engine is running.
3. The fuel mixture should be adjusted as
follows: The low-speed fuel mixture is too
rich if, when opening the throttle rapidly,
the engine emits smoke and “stutters” or
“stumbles.” Correct this by rotating the
SetRight adjustment bar clockwise in small
increments. Continue this process until the
engine transitions smoothly from low rpm
idle to high rpm without hesitation upon
opening the throttle rapidly.
4. The low-speed fuel mixture may be too lean
if the engine stops at the lowest idle position
or it stops when the throttle is rapidly opened
from the idle position. Correct this by rotating
the SetRight adjustment bar counterclock-
wise in small increments until the engine
transitions smoothly without hesitation upon
opening the throttle rapidly from idle.
Setting the Needle Valves