What kind of floats do you have, brass or plastic? The setting spec differs for each, and your 23.5mm setting is pretty far off from both, lol. Stock, a 1980 carb set would come with brass floats, but someone could have swapped plastic ones in. The setting spec for the brass floats is 27.3mm ± .5mm, and for the plastic floats, it's 22mm ± 1mm. Depending on which type of float you have, your 23.5mm setting will make the fuel level too high (brass float) or too low (plastic float). The float level being off can make the bike run rich (too high) or lean (too low). I'd say it's best you revisit the floats and set them correctly. No sense trying to re-jet and tune the carbs with the float levels messed up like that.
Is your bike a Canadian bike with the Canadian carbs? I ask because if it is, it should have an adjustable needle and may be jetted slightly different than the U.S. models. Here in the States, our BS34s came with a fixed (non-adjustable) needle, 132.5 mains, and 135 air jets. Yours may have 130 mains and 130 air jets. You'll need to check that. The re-jetting changes needed will probably be the same as far as number of size change, just the size may differ depending on what you've got to start. For just the mufflers, one up on the mains would probably be good. Once you add pod filters, two up on the mains would probably be good, along with a step up one on the pilots.
I also play around with the pilot air jet size, reducing it 2 if I don't change the pilot, only one if I do. You may not need to do anything with yours if it already has a 130 in it.
I have the black plastic ones, so I'll aim for 22mm. My bike is Canadian and I would have guessed the carbs are bone stock but I definitely can't say for sure, though, I do know the floats do have the sleeve for a better fit on the pin, either way I'll adjust the tang accordingly.
The bike came with 132.5 mains and 135 air jets and I'm really not sure if my needle is adjustable or fixed, I'm assuming it would be obvious if it was adjustable so my guess is that it is fixed, the only thing I didn't take apart when cleaning the carbs was the needle from the slide, maybe I need to do that to know if it is fixed?
It sounds like with just the muffler change I'll up the mains to 135 and leave the rest as is, if it needs another change I'll look at upping the pilots one size and/or reducing the air jet.
This is the first set of carbs I've torn into so the help is much appreciated!