Fred;
I performed the same procedure but went ahead and removed the two screws.
The rear housing fell to the workbench before I could catch it. The housing contains a spiral spring that indexes with the speedo needle.
I guessed wrong that the needle should index after making one revolution on the spring. (A metal tab limits the range of movement)
I reassembled everything and found that the speedo now reads low.
It has to come out again and apart and the needle (i think) should be indexed on a "relaxed" spring.
It would be great if a professional Stovebolt speedo person would throw out a few words of wisdom before I tear into this again.
Mike