OK. That helps a lot. Let's assume that the guys at the shop didn't screw up the carbs (I'll come back to that later) but DID screw with the idle. Unlike the advice you may have heard from the TA/SM guys with 270 degree ignition, you have a 360 degree twin, firing with a wasted spark sequence, and you do not really want a "bouncy" idle. You might like the sound, but the bounce is really a small one of those hiccups! So, your idle is probably set quite a bit lower than it was before you took it to the shop.
Try this. Get the bike good and warm, at least a ten mile run, come home, let it idle and turn the idle down to where it stumbles, not hiccups, but stumbles. Then turn it the other way until it seems to be running a bit too fast. Repeat until you get it to the spot where it never stumbles. Then, INCREASE the idle a bit more- until you think it might be just slightly too fast. If you had a tach you would find you are at about 1200 rpm. With a slightly fast idle your bike will be much more responsive on take off, will not stumble, or hiccup, and will not give you heartburn thinking it might quit.
If that works, fine; problem solved.
If not, then before I'd look for something electrical I would suspect that in the process of working on your carbs the shop boys stirred up some gunk (scientific term) in the float bowls, or, if they took the carbs off they might have disturbed some of the junk in the bottom of the tank or in the gas line.
If you promise not to laugh I'll tell you how to solve that one yourself, without having to touch anything. Go to an auto supply and buy a bottle of MMO (Marvel Mystery Oil). Following the directions on the bottle mix the right ratio of MMO to gas into the next three tanks of gas. Be precise, or err on the side of more rather than less. Too little won't do any good.
It isn't really as snake oil as it sounds. Racers have used it for years. I've used it when I raced and in my street bikes for over 50 years, not all the time, but when small junk plugged up the fuel system, or when the bike didn't run as smoothly as it had. MMO is the best solvent on the market, will not hurt your bike, and will disolve any small particles of hydrocarbon in your system, even paint chips!, and then you burn them up and send them out the exhaust. There are other much more expensive solvents on the market, like Techron, but they are basically MMO in a small bottle with a big price tag.
I hope the first thing works. If not, try the second. And if that fails take it back to the shop and tell them that they screwed up your bike and you want them to make it right.
Good luck,
Monte
