needle and listen as the engine runs progressively faster and smoother. At some
point it will be nice and smooth and really pumping, then start to sag (lean), you have
just gone through peak. Stop immediately and open the H needle until the engine
passes over peak and just starts to fall off (rich) again. Leave the H needle for now.
With the engine at its slowest
reliable
idle, open the throttle briskly. The engine
should throttle up nicely – if so start leaning (clockwise) the L needle 1/8 turn at a
time until the engine hesitates /stumbles when opened. The L needle is now too lean,
open it (anti-clockwise) 1/8 turn and try again until the engine throttles up smartly
without stumbling. Each time the L needle is closed a bit, the engine will idle faster,
bring it back down with the mechanical idle stop.
Now go back to full taps for few seconds and reset the H needle for just-on-peak –
then back to the L needle for a steady idle.
Set the mechanical idle stop for a reliable idle (1,300 – 1,500 rpm)
Listen to the engine during flight – if it appears to sag off during full throttle flight
(maybe in a climb), land without delay and richen (anti-clockwise) the H needle1/8
turn.
If the engine burbles a bit in the mid-range, the L needle may need to be closed a bit.
Check again that the engine does not stumble when throttled up smartly (lean on the L
needle).
Trouble Shooting
Motor won’t start:
Flooding: - Over choking can cause flooding. Clear as above.
Low ignition battery voltage - check battery voltage (should be at least 5.0+ volts)
as well as all ignition connections, wiring, and switches.
Check fuel flow and look for kinks, pin holes or other damage.
Does fuel move toward the carburetor when the prop is flipped with the choke
closed? If not, is the choke butterfly closing completely? Is the carburetor or
carburetor mount loose causing an air leak?
Is the throttle set at idle or slightly higher after engine “barks” and choke is
opened?
