Fuel and Oil Mix
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For the DA120, use Premium pump gas, such as 91 to 93 octane.
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We recommend purchasing your fuel from “name brand” gas stations. We have seen problems with
cheaper gas from some discount type outlets.
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We recommend filtering your fuel between your fuel container and your plane’s fuel tank. A high
flow filter, or clunk/filter, between the tank and motor is also a good idea.
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Make sure the plane’s tank is well vented and the fuel clunk moves freely.
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Use of any other fuel or additives such as nitro formulas, aviation gas, white gas, etc., can
harm the motor and void the warranty.
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Do not use silicone sealers on the fuel system. Gas can break it down and carry it into the carb.
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We recommend a high quality synthetic oil. As for the brand of oil, there are many good ones on the
market. Some oils, and their mix ratios, that Desert Aircraft recommends are: Red-line Two Stroke
Racing Oil (40 to 1), Motul 800 (50 to 1), and Stihl HP Ultra (50 to 1). These oils can be found at
most motorcycle or chainsaw shops.
Break-in
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We do not recommend breaking the engine in on a test stand. The stationary load and lack of air
ducting can lead to engine over heating.
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Special break in props are not required. Just don't start with something beyond the recommended
sizes. Over loading the engine creates excessive heat. Peak rpm should be over 6,000 during the
break-in process.
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Adjust the needles as needed and give the engine a few easy flights. The needles may need
adjustment as the engine settles in and when other things change such as different props, exhaust,
weather, and altitude.
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The engine should run well from the beginning and improve as flight hours accumulate.
Recommended Props
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Always check and
tighten prop bolts
before each flight! Loose prop bolts allow prop movement,
which will shear the bolts.
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Always use the correct length prop bolts. If a spinner back plate is not used, the prop bolts may be
too long and can bottom out in the hub before they fully tighten against the prop washer.
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While special break-in props are not generally required, they can help speed up the break-in process
and reduce the risk of over loading/heating the motor.
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Some recommended props are:
Wood: 28x10, 29x10
Mejzlik Carbon: 27x12TH, 28x12, 29x10S
Mejzlik Carbon 3 blade: 26x12, 27x12TH
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The DA120 has a very wide power band. The "normal" peak operating rpm for break-in is 6,000 to
6,500 rpm, and 5,700 to 6,800 rpm for normal aerobatics after break-in.
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Smaller diameter props with more pitch, especially 3 blades, can reduce tip speed and noise.
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Always use a drill guide to drill your props.
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Always check the balance of your prop.
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For safety, we recommend painting the tips of your props (front and back) with a bright color,
especially on black props.
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