28 degrees total advance. However, many magnetos have a built in advance that you will either have to measure with a timing light on a a running engine and duplicate, or else carefully measure the coil and flywheel mounting positions and reverse them for the "backwards" running engine. Fabricating a new, sturdy mounting for the coil is not easy. I highly suggest that you just convert to CDI electronic ignition. Then it will be a breeze. Ignitions are only around 50 bucks nowadays, and make for an easier starting, nicer handling engine.

AV8TOR