The tank they supply is about 380cc or like 14 oz. Just a bit small. How efficient is that 160 twin?. If you go Moki, use the 1.8. It will have plenty of power, about the same as the 160 FX, and more fuel efficient than the 2.1. My Moki 1.8 and OS 160 use about the same amount of fuel and a 16 oz tank is fine and what I run on them. My 160 runs better and is 8 oz lighter than the Moki.