The 78Ks came with 110 mains which was probably a nod to the EPA. These are pumper carbs so the accel pump would probably cover up for any lack of response.
The main jets are slotted and can me taken out with a screwdriver, and the size may be readable with a mirror. The PO put 120s in mine and I have not found the need to change them. They have nothing to do with idle and everything to do with passing an 18 wheeler on a steep mountain road.
The idle jets are pressed in which was another nod to the EPA, but they can be carefully pulled out and cleaned, and it usually plugged up if you read through the threads.
If I were you I would pull the carbs and give them a good and proper cleaning. I had mine off 3 times in 3 years before I finally did the job properly. That was 6 years ago and she runs great.
I would suggest you get some kits from Sirisonic or some one else. Take the rack off and give them a good cleaning. You will need a few strands of copper wire or high E guitar string and pass it through every hole you can find. Pull the pressed in idle jets and clean out all the side holes - the jet is at the bottom. After you pass the wire through, use some spray carb cleaner blow out the debris.
Now, the accel pump only holds probably less than a 1/4 teaspoon of gas, and it spoils really quickly becuse there is so little of it, so unscrew the bottom and flush that out also.
You see there is no quick fix with carbs other than a float level that goes whacky. If you want to spend the time, you will get a good result, I know I tried all the quick fixes and they failed.
Once you have the carbs sorted out, you will have other things to tinker with to improve the bike.
