Chris, if you look about for a later model Victa with a straight intake, it should have a bigger jet in it.
The 125 had a circle in the face of the jet.
The 160 is plain on the face.
The straight inlet jet has two circles on the face.
These will only work in a LM carb. LM jet will not work in a G4 carb. Had a mower in the shed early in the week that was over revving to the moon, worked out that it had a G4 carb with LM internals and jet. Swapped it all into a LM body and it was fine, better than a bought one.
If you have a G4 carb (which it probably does) you will need to have a look in the forum for the jetting info for the twin. It uses a bigger jet i think.
I want to do a hop up on the full crank to go in a little gokart. I figure it will rev harder and be a bit more forgiving with being over revved due to the design. Just not real sure with how to carb it. If i should switch to a motorbike style carb, I really would like to to be able to rev up and down freely. Plastic carb will do that but it will wear out eventually.