How to Set Timing w/Vac Advance

This is a guide to making timing advance adjustments.
A Sun distributor machine such as a Model 503 would be the preferred method.

1. Disconnect the vacuum line from vacuum advance control to the vacuum port on bottom of carb and plug the port on the carb.
2. Set the idle speed to 600 RPM.
3. Check the initial timing and set it at 8 degrees or to factory spec.
4. Raise the engine RPM to 2000 while checking timing again for mechanical advance (centrifugal advance) should be close to 22 degrees.
5. Re-connected vacuum line between advance control and vacuum port on carb. Hold the engine RPM at 2000 and observe the timing.
6. Using an Allen wrench adjust the internal screw on vacuum advance control until you dial it in where you want it.
7. Re-check the timing with engine at 2000RPM and vac advance hooked up you should see a total advance of 34 degrees.


8 degrees initial timing
22 degrees with mechanical advance (@ 2000rpm)
34 degrees with mechanical and vacuum advance (@ 2000rpm)

You can look up the specs for your engine and adjust as needed.
The counterweights are adjusted by slightly bending the spring tabs under the breaker plate.