I've got one of the same 7M carburetors. I bought a complete used engine to get the carburetor. I used the carb on a Nelson short stroke .40 racing engine. The round barrel that goes into the crankcase had to be modified extensively, so that the carb will no longer work on the OS .60 it came from. I'd like to find a serviceable carb body to return my carb back to stock. Finally these 7M carburetors are great carbs. They were developed for helicopters, and essentially have high speed, mid range, and idle capability.