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Magneto-Ignition Timing Devices

 Magneto-Ignition Timing Devices

Built-In Engine Timing Reference Marks

  • Most reciprocating engines have timing reference marks built into the engine. The timing reference marks vary by manufacturer.
  •  When the starter gear hub is installed correctly, the timing marks are marked on it that line up with the mark on the starter.
  •   On an the engine that has no starter gear hub, the timing mark is normally on the propeller
  • flange edge.
  • The top center (TC) mark stamped on the edge aligns with the crankcase split line below the crankshaft when the No.
  • 1 piston is at top dead center. Other flange marks indicate degrees before the top center.
  • done by checking and adjusting the ignition points to open at the E-gap position.
  • The chamfered tooth should line up (reference timing mark for the magneto) in the middle of the timing window. The magneto is set to fire the No. 1 cylinder. Remove the most accessible spark plug from the No. 1 cylinder. Pull the propeller through in the direction of rotation until the No. 1 piston is coming up on the compression stroke.
  • This can be determined by holding a thumb over the spark plug hole until the compression air is felt. Set the engine crankshaft at the prescribed number of degrees ahead of true top dead center as specified in the applicable manufacturer’s instruction, usually using the timing marks on the engine.
  • With the engine set at a prescribed number of degrees ahead of true top dead center on the compression stroke and with final movement of the engine stopped in the direction of normal rotation, the magneto can be installed on the engine.
  • Some engines have degree markings on the propeller reduction drive gear.
  • To time these engines, the plug
  • provided on the exterior of the reduction gear housing must be removed to view the timing marks. On other engines, the timing marks are on a crankshaft flange and can be viewed by removing a plug from the crankcase.
  • In every case, the engine manufacturer’s instructions give the location of builtin timing reference marks.

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