1. Check centrifugal governor.
2. Connect a vacuum pump to the regulator.
3. Run the engine up to 2500 rpm and measure the centrifugal advance in degrees from the point "0" on the plate.
4. Set the vacuum in the range of values given in the characteristic and bring the engine up to a rotation speed of 2500 rpm.
5. Measure the spark advance and subtract the previously measured centrifugal advance to give the vacuum advance.