this one is a .16 and has 1hp, 2.43cc i believe, the .18 is 2.3hp and is around 2.92cc, .21 is 3.2hp and 3.45cc, and they are really cheap on ebay they go around 60$, and here is pics of mine, is side exhaust, rotary carb, and about the clutch thing i dont know so good but its a short tread one i believe i post a pic.