User Manual

PAGE 10 OF 22
fly the model with the mixture on the rich side still. This allows for good cooling. Avoid running the engine in during
hot ambient temperatures.
• You want to give the ring a chance to wear in to a more perfect fit to the cylinder wall. Use of petroleum
based oil along with light loads and vary the throttle during the first few gallons of gas helps here.
• You don't want to overheat the engine. A new engine tends to develop more heat than one that's run in. No
full power verticals or hovering, as there is less cooling air and high power = high heat conditions.
• Make sure the engine is running efficiently. Proper (not overly rich) fuel air mixtures and proper gas to oil
ratios help here. Let the break in oil do its job.
Tuning Hints
Running
rough
Popping, spitting, spluttering, burbling.
Goosing
Opening the throttle from idle to full very quickly.
Lean
The term lean means that there is less fuel being delivered to the engine from the carburettor
for a given throttle setting. The engine will run faster, smoother and hotter as the mixture is
leaned, provided that it is not leaned too much.
Rich
The term rich means that there is more fuel being delivered to the engine from the
carburettor for a given throttle setting. The engine will run slower, cooler and less smoothly
and will probably foul the spark plugs if it is too rich.
Low Needle
Process
Keep in mind the low needle affects the high one but not the other way round.
The low needle should be set as lean as possible without displaying any of the bad symptoms
mentioned below. First get it to run smoothly at idle, then try goosing it to about 1/3 throttle.
Adjust until the transition is smooth.
Symptom
Too Rich:
Runs rough and shakes badly. Burbles in midrange and smoothes out at full
throttle Engine will transition slowly May die after idling for a long period
Too Lean:
Hard to start Won't decelerate (hangs at higher revs for a while) Dies when
'goosed' to full throttle
Warnings
Setting too lean may cause a dead stick when opening throttle after a long downline.
High Needle
Process
Keep in mind the low needle affects the high one but not the other way round.
Bring the throttle up to high and back the high needle out till it runs rough / rich. If you can not
get the needle to produce an over rich condition then you have insufficient fuel flow (example:
tubing may be too thin). Fix it and then restart the tuning process.
The high needle should be set to gain maximum RPM without overheating. When running in it
should be set slightly rich.
Measure the RPM and slowly close the needle as long as RPMs continue to climb. If RPMs
flatten out or fall then back off about 1/16 of a turn.
Test the high needle setting in the air by pulling vertical and flying some loops. If it loses RPM
it is probably set too lean. Open it about 1/16 of a turn and try again.
Symptom
Too Rich:
Full throttle blubbers, cleans up only on uplines Will not
develop full power
Too Lean:
Runs hot Sags on uplines May die in flight Will not run at
full throttle
Warnings
Setting too rich may cause the engine to generate carbon deposits and foul the spark plugs.
Conclusion/Confusion - Mixed Symptoms
Runs hot
May be caused by high needle being too lean and/or by timing being too retarded.