Genuine Mazda MX-5 Miata Exhaust Valve

Mazda MX-5 Miata Exhaust Valve Parts and Q&A

• Exhaust Valve
  LF02-12-121F
  Q:

  What procedure applies only for adjusting Exhaust Valve and Intake Valve clearances on Mazda MX-5 Miata?

  A:

  This process is for 1999 and newer model years only. Take off the valve/rocker cover and turn the engine until TDC is obtained on the compression stroke on cylinder No 1. turn the engine only in the clockwise direction from the front. Using feeler gauges, measure the clearances of the specified valves between the base of the cam lobe and the lifter. Note all four clearances. Note that the clearance for the intake and exhaust valves are different. Once more, turn the crankshaft 360 degrees clockwise to place number 4 cylinder on TDC on compression, and check the clearances on the specified valves. In the case of the models aged between 1999 and 2005, if any of the valve clearances are found to be out of specification, try to turn the crankshaft pulley until the camshaft lobe above the first valve to adjust points upward. The notch in the valve lifter must then be positioned towards the centre of the engine. The valve lifter is then depressed with special tools. Take out the adjusting shim and measure thickness with a micrometer. To determine the proper thickness of a replacement shim, use this formula and pick a shim that is as close as possible to the calculated valve clearance. Place the new adjusting shim, and check clearance with a feeler gauge. Repeat as necessary until all out-of-clearance valves are adjusted correctly. On cars built from 2006 onwards whom ever needs adjustment, won't be able to change the lifters without removing the camshafts over the affected valves. If the valve clearance is found to be small, install a lifter with a thinner head and if it is large, a head of a thicker thickness is used. Use a micrometer to measure the lifter thickness if needed. Once you've installed the lifters of the correct thickness, reinstall your camshafts and go through the adjustment process again for any clearances that remain out of spec. Documenting the lifter thicknesses fitted at different positions will help later to make any adjustments required in the future. Advance purchases of lifters required can be made once clearances and existing thicknesses are known.