12
1. With the engine started and warmed up,
open the throttle fully and note the rpm.
Listen to the engine.
a. If the engine occasionally mis-fires but
maintains a fairly constant rpm after 5
seconds, your engine is rich. Reduce the
throttle to idle and turn in (clockwise) the
high-speed needle 2 clicks. Repeat this
until the engine stops mis-firing.
b. If the engine does not mis-fire and the
rpm steadily decreases from the highest
rpm achieved when you opened the
throttle, it is lean. Reduce the throttle
to idle and open (counterclockwise)
the high-speed needle 2 clicks. Repeat
this until the engine maintains the rpm
achieved when the throttle is wide open
Your goal here is to achieve a good
transition between high and low speed,
and that the high-speed rpm will be
steady on the ground.
2. Fly your aircraft for the in-air testing.
a. During flight, if the engine seems to slow
down or sag when climbing, your engine
is running slightly lean. Land the
airplane and open the high-speed needle
valve 2 clicks and take-off again.
b. During flight, if you hear the engine mis-
firing occasionally in level flight, this is an
indication it is running too rich. Land the
airplane and close the high-speed needle
valve 2 clicks and take-off again.
c. Repeat the above process until your
engine performance is steady and
repeatable. This high-speed needle
setting should not change more than
+/– 1–2 clicks in the future when using
the same propeller. If it does, something
is wrong in the fuel delivery system and
should be investigated.
If you are using onboard telemetry and have
a temperature monitor on the head of your
engine, your readings should be between
200°F (93°C) and 270°F (132°C). If you see
consistent temperatures above 280°F (138°C)
you should land your airplane and add baffling
to your cowl in order to increase cooling to
the engine. See the Telemetry section for
information on the proper positioning of your
sensor.
High-Speed Needle Adjustment
Because of the small amount of fuel actually needed for this engine, needle adjustments need
to be made in small increments. It may take 5 seconds or more before you will notice a running
change in your engine after making it. Be patient. Use a tachometer, this is a very important part
of properly setting your high-speed needle valve.
The procedure below is for ground setting the needles prior to flight. The final adjustments need
to be made after noting the performance in the air.
