Carb – spark sync 1952 Big twin

[joecb]

Hello, I’m helping a friend with a 1952 Evinrude 25 hp Big Twin, A question on setting the spark cam to throttle sync. There is no mark on the cam to indicate where the throttle should begin to move. So , how do you set this?? At what point on the cam should the throttle begin to move?

Joe B

---

Attachments:

[chris-p]

The RD 12 and RD 13 were the only years like this.

The RD 10 and RD 11 had an index mark on the cam.

Then in 1951 for the RD 12 and the 1952 RD13 you are working on, they omitted the index mark, and added the "depression" in the cam. This depression completely closes the butterfly when you retard the spark. IT should drop into this depression when the throttle is at STOP.

Then in 1953 for the RD14, things were improved in my opinion with the addition of a roller. The roller prevented wear on the cam, and allowed for smoother acceleration and operation.

[joecb]

Thanks Chris, that’s what we needed

Joe B

[Author]

Posts