The CS-1089 uses a rubber boot to attach the carb. It would not be my first choice for that reason. Wouldn't the CS-400 shortblock (SB1089) be a better choice for a 40cc? It has a flat faced carb insulator attachment. I see Farmers Echange has those for $154, I bet you could get a quantity discount. It would be like a baby BME-50. I would not be surprized if some the parts are the same as the 50.

"The BME guy in China Springs TX has not been on this site in almost 2 years." Oh geeze, I saw that after I looked this stuff up. Maybe it will be usefull to someone?