Needle Adjustments
(Cont'd)
•
Adjust the Low End needle until you achieve a smooth idle and a reliable transition to high throttle.
Generally if the motor “stutters” or “coughs” in the mid range or when the throttle is advanced, the
low end needle is too rich and possibly even the high end needle. If the motor dies quickly, the low
end is probably lean.
•
Don't set the needles overly rich to protect the engine. Operating the motor overly rich not only
reduces power, it creates other problems such as poor transition, pre-mature carbon build up, fouled
plugs, excessive exhaust residue, sticking rings, airframe vibration, and overall rough running.
Trouble Shooting
Motor won't start:
•
Check battery voltage (should be 5.0+ volts) and all ignition connections, wiring and switches. Wires
can break from vibration near connectors. Check and/or swap out regulator.
•
Does fuel move towards the carb when the prop is flipped? If not, check tank venting, clunk position,
and fuel lines for leaks. Is the choke plate closing completely? Is the carb or carb mount loose
causing an air leak? Air leaks on the engine usually show as fuel seepage.
•
Is throttle set at idle or slightly higher after motor “pops” and choke is opened?
•
Make sure prop is flipped over with authority. The ignition won’t fire at low speed.
•
If a lot of fuel drips from carb, the motor might be flooded. If so, remove and dry, or replace, the
spark plug. Try starting again without using the choke. If engine doesn't fire after several flips, try
choking again.
Other issues:
•
RPM won’t go over 3,500 to 4,000: The connector between the ignition module and ignition sensor
may be plugged in backwards. Check the color of the wires leading into the connectors to make
sure that the polarity is correct.
•
Broken prop bolts: In order for bolts to shear, some type of side loading (shear) movement is
usually required. If the bolts are tightened correctly, nothing moves and prop bolts will rarely break.
It’s a good idea to replace prop bolts routinely. Check prop bolts before each flight!
•
Excessive vibration: Check that the low rpm needle setting is not too rich. Check prop and spinner
balance. Check the firewall and motor box area of the aircraft for movement, poor glue joints, etc.
This area must be rigid! Some aircraft on the market are lacking in this area and may require
additional glue and/or structure. Poor quality or contaminated fuel can cause rough running.
•
Pink or purple colored cylinders: These colors indicate engine temperature has been too high at
some point. Check that needle settings are not too lean, air flow for cooling is sufficient, and oil/gas
mixture is correct.
•
Engine starts backwards: 2 stroke reed valve engines can generally run in either direction. Make
sure the prop is flipped forcefully through the compression stroke. Without enough force, the prop
may "bounce" off compression and run backwards.
IF ANY PROBLEM PERSISTS, PLEASE CONTACT DESERT AIRCRAFT FIRST!
We designed and manufactured your engine and have built, serviced, and analyzed
thousands more. We cover your engine’s warranty, not someone at the field or a stranger
on the Internet. Please give us the opportunity to help first!
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