How to Measure Motorcycle Ignition Timing

Written by william machin
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How to Measure Motorcycle Ignition Timing
Motorcycle inginiton timing is measured in degrees. (Jupiterimages/ Images)

Motorcycle ignition timing is the coordination of the intake valves during the piston combustion stroke with a spark from the ignition coil. The engine is timed using a strobe timing light to line up marks on the timing plate at a specific degree. This is known as the angle of the timing. The angle at the top-dead-centre (TDC) mark on the timing flywheel is in line with lobes on the engine's camshaft that open and close the intake valves. You measure the ignition timing on a motorcycle using the information provided in your service manual.

Skill level:

Things you need

  • Service manual (year and model of your motorcycle)
  • Circular protractor (angles in degrees)
  • Spark plug wrench
  • Metric socket and ratchet

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  1. 1

    Roll the motorcycle forward and put the transmission in the highest gear. Park the motorcycle on the centre stand or elevate the rear tire off the floor with wood blocks under the motorcycle frame.

  2. 2

    Remove the spark plug wires by hand. Remove the spark plugs counterclockwise with a plug wrench. Removing the plugs eliminates engine compression, allowing you to rotate the rear wheel and turn the engine's timing flywheel with the bike in high gear.

  3. 3

    Locate the timing cover at the side of the engine crankcase. On most bikes, the cover is on the same side as the rear brake pedal. Remove the cover bolts counterclockwise with a metric socket and ratchet or a metric nut driver.

  4. 4

    Look inside the timing housing and notice the viewing hole and vertical indicator at the upper edge of the timing plate. Rotate the rear wheel of the bike forward by hand until the timing marks appear in the window. Rotate the wheel forward or back a bit as needed so the timing marks are directly in line with the indicator at the viewing window.

  5. 5

    Open your service manual and go to the ignition timing section. Depending on the motorcycle manufacturer, the manual either has a set of numbers in degrees next to TDC, or a diagram of the timing plate with degrees and the TDC mark. Locate the set of numbers or degrees that refer to "Intake." This is the degree of timing for the intake valves.

  6. 6

    Hold an angle protractor in front of the timing plate. Rotate the protractor until "Zero" lines up with the indicator at the timing window. Make sure the timing marks on the flywheel are still aligned with the indicator.

  7. 7

    Read the mark on the protractor that lines up with the intake valve (IN) mark toward the front of the timing plate. The front of the plate is toward the front wheel of the motorcycle. The protractor should read the same degree of intake timing as given in your service manual.

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