You would need to able to set the timing withinstructions that come with the ignition andyou'd have to lock the timing/sensor ring into a fixed position that facilitates the correct timing setting. Then remove thetiming link rod from the belcrank, the belcrank stays forthe throttle.

To lock thetiming ring you would drill through ittowards the crankcase with a #43 drill bit, stop the drill just as it touches the case, tap the hole for a #4-40 socket headed cap screw that's about 1/8" longer than needed to reach the crankcase. The bottom of the hole will be void of threads because the tap has to stop at the case and can't go through, file thelast 1/8" - 1/4" of the set screw O.D.down a little so it will reach the crankcase without binding to tight and lock the ring in position. Ideally you would be able to pull the hub and timing ring off to perform the proceedure but it's not a requirement.

It doesn't matter if you get a replacement from me or another, if it's an auto advance unit the above procedure would be necessary. If you want to replace it with another fixed timing unit give the email address I posted for youa yank and leave the sensor ring as is.