Thanks for your patience Rob, as you know (but I had forgotten) I've already made that test myself with the the Ruixing one and the Keihin one, and got the same results as you did. So the Huayi idle jet is slightly smaller than the Ruixing, which in turn is a bit smaller than the Keihin. The Keihin is officially 0.38 mm, but for the others we don't have official figures and can only guess, since both of us only have jet drill bits in size intervals of 0.05 mm. With the idle jet it doesn't matter much because you can adjust the idle mixture screw to compensate. With the main jet you can't adjust anything to compensate, and the Ruixing one is approximately 0.60 mm in their GX120 version. In the Keihin, the main jet is 0.60 mm for the GXV120, and 0.55 mm for the GXV140. I haven't measured a GXV160 one. So, at this stage there is no great difference in the jetting for the GX120 versions of the Keihin (Honda) and Ruixing (chonda) carburetors. The Huayi, presumably another chonda, so far has a compatible idle jet, and we don't yet know about the main jet. So far, our starting-off guess that the chonda bits are mostly interchangeable with Honda bits, is standing up fairly well. However we do know there are bits that don't interchange - in particular, some flywheels. I'm pretty sure the ignition modules for chonda and Honda will usually interchange, at least on the GXV140 and GXV160, but I'm not so sure about the GXV120. I have a vague recollection that the GXV120 cylinder block does not have the dual set of ignition module mounting holes that the GXV140 and GXV160 have. Would you mind having a look on the genuine GXV120 you are working on, and see if it has the three module mounting holes, or only two? The two holes would fit an N type module, but you need the extra, offset hole to fit an A type module. I'd check it myself but I don't have a spare GXV120 block any more, having thrown out a couple of worn-out ones.
