Many, many carbs do have the same mounting size though. It's just a matter of locating one that isn't in use somewhere; start asking the club members what they might have that you can try. I found a Tower Hobbies 75 carb that worked great in my Super Tigre 90 for example. There are lots of OS 61's out there, dead and alive. I don't remember if they all had the rear needle valve or not though, but might be a drop in fit. Good luck, just a matter of time.

Ernie Misner