I have a 5 star, missing some parts, but have made a new kingpost. I was told I need a 19t sprocket by another owner, I have 13'' stroke rams & a 1.25'' chain pitch. To get 180 degrees it would point to a 20t sprocket (10t x 1.25'' = 12.5'' )
So either the Gopher went 200 degrees from new or that different metric rams were used on some models.
I can no longer contact fellow owner Mark (pedrix 99 in France) as the email no longer works, he helped me much in the past, let me know if you are Ok if still out there