| Tuning is simply adjusting your engine
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| | changing to higher pitch
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| for peak performance. The factory-fresh
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| | Leaner still: little smoke, max rpm
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| settings may be a good starting point.
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| | reached
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| However, you may need to compensate for
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| | Too lean: very little smoke, max rpm can
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| higher altitudes, or for temperature
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| | be heard falling off. Open the needle
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| changes with the seasons. Changes in fuel
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| | valve up 20 or 30 degrees from this
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| type or engine wear, may also require a
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| | point. If you have a tachometer, open the
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| tune-up.
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| | needle about 300 rpm less than max.
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| Relatively more fuel to air is known as a
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| | 5) Still at high throttle, perform the
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| "rich" mixture, while the opposite is
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| | pinch test. Briefly pinch then release
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| known as a "lean" mixture. A lean mixture
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| | the fuel tube going into the carb. If the
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| generates more power, but also generates
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| | engine momentarily speeds up, then slows
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| more heat. Too much heat could damage the
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| | back down, you're done. If the engine
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| engine. A rich mixture generates less
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| | does not speed up, or quits, then it is
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| power and less heat. Too rich and the
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| | too lean; richen the needle some more.
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| engine might quit while you're flying.
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| | 6) Now throttle back to idle; let the
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| The popular twin-needle carburetor has
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| | engine idle for a couple minutes.
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| two needle valves. The high speed needle
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| | 7) Now perform another pinch test. This
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| controls the total fuel flow into the
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| | time pinch and hold the line. The engine
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| engine, and affects the engine's behavior
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| | will want to speed up and die. If it
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| from half to full throttle. The low speed
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| | speeds up immediately, it's too lean,
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| needle tends to have more of an effect
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| | richen the low speed needle. It should
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| from half throttle down to idle. Both the
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| | take 4-6 seconds to speed up and begin to
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| low and high speed needles can be
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| | die. Any longer and it's too rich.
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| richened (counterclockwise turning), or
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| | 8) Also check the throttle transition.
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| leaned (clockwise turning).
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| | With the aircraft secured and engine
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| Tuning Procedure:
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| | idling for a couple minutes, advance the
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| 1) Start with the factory recommended
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| | throttle quickly to fully open. If the
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| needle valve settings.
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| | engine hesitates, the low speed mixture
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| 2) Start the engine.
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| | is too rich.
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| 3) With the engine or aircraft secured,
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| | For more information about Model Airplane
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| open the throttle to full.
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| | Engines, visit the RC Airplane Advisor -
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| 4) Lean the high speed needle slowly and
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| | Model Airplane Engines.
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| watch and listen:
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| | This article may be reprinted if proper
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| Too rich: lots of smoke, low pitched
| |
| | credit is given and all links left
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| sound
| |
| | intact.
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| Leaner: reduced smoke, sound starts
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| |
|
