Maintenance
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Being a high performance 2 stroke engine, certain parts can wear quickly. Under normal operation,
pistons, piston rings, needle bearings, spark plugs, etc. may need occasional non-warranty
replacement to insure peak performance. Other factors can hasten the need for replacement parts
such as ingested dirt and debris, exceedingly high temperatures due to improper lubrication, airflow,
improper needle adjustments, excessive prop loads, etc.
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If the engine has been involved in a crash or severe prop strike, inspect it carefully for any signs of
damage before operating the engine. Make sure nothing was ingested into the engine. Check that
the prop hub rotates freely and without any "run out" or wobble. Look for any signs of cracks in the
case, especially near the motor mount area. If the spark plug cap shows any damage, do not
operate the ignition. If there is a short inside the cap, it can cause damage to the ignition module.
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Screws can come loose! After a few flights check that all screws are secure. Periodically check that
all screws are tightened to the correct torque rating. It's recommended to replace, rather than re-use
the red aluminum screws whenever they are removed. If exhaust flange screws become loose, the
flange face and threaded holes can be damaged to the point where the header or muffler won't stay
tight and the cylinder needs to be repaired or replaced.
Torque specifications
Size Torque setting
Spark plug: CM-6, 10mm 90 in. lbs.
Steel prop bolts: M5x 45mm 75 in. lbs. / wood props, 90 in. lbs. /carbon props.
Aluminum crankcase bolts: M5x16mm 70 in. lbs. (One use only, do not re-use)
Aluminum cylinder base bolts: M5x16mm 70 in. lbs. (One use only, do not re-use)
Aluminum carb mount bolts: M5x75mm 8 in. lbs.
*
(Low torque value allows re-use)
.
*Caution:
Care must be taken to not over tighten the carb mounting bolts. Over tightening can
distort and damage the injected molded reed valve parts and rubber gaskets.
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Use a 4m hex wrench for all M5 cap screws.
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For spinner mounting, the crankshaft extension is threaded for M5 screws. In this application
(steel to steel) the 10-32 SAE screws supplied with most spinners will work fine in the M5
threaded hole.
Do not substitute 10-32 screws for any other screws on the engine!
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Inspect the engine periodically for any signs of fuel seepage. This can indicate an air leak which
can create a lean fuel/air ratio, which in turn can cause erratic running and engine damage. If
tightening the appropriate screws does not cure the problem, contact Desert Aircraft.
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After prolonged use, carbon deposits can build up on top of the piston and on the combustion
dome of the cylinder. Great care must be taken when trying to remove these carbon deposits to
avoid damaging the parts. Once an attempt to remove carbon has been made, the task must be
completed, as any remaining carbon may be loosened and can dislodge while the engine is
running. This can damage the engine and/or bridge the spark plug.
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If the engine is going to be stored for a long period of time, it is recommended to run a few
minutes worth of non-ethanol fuel through the engine. This can help reduce the chance of
corrosion from water associated with ethanol in gasoline. Often larger gas stations offer "race
gas" or other high octane ethanol-free gas.
Manuals may be updated with additional tips and trouble-shooting info from time to time. Please check
our web site, www.desertaircraft.com, for current downloadable manuals and updates, or contact Desert
Aircraft.
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