going over the engine shelf decided to check the Irvine 36 against the Irvine 25 ( both UK) jetstream carbs the 36 goes back a few years mount same size on both
the 25 weighs 346Gm, the 36 362Gm, with mufflers stock Irvines only a 17 Gm difference for the displacement when you go to the 40 its 498Gm thats a 136Gm
weight increase to go from a 36 to a 40 as I remember the 36 was very close in power to the 40 martin