[fizzwheel]

Are you using fresh fuel, or fuel that was stored over the winter, if you arent using fresh fuel try and tank of it and see if it runs any better then. Unleaded doesnt keep well and it goes off over time. I've had similar trouble with my curvey SV after being sat for 6 months, ( wouldnt start and when it did it idled like a bag of cr*p, didnt run properly ) Fresh fuel cured that.

You could try cleaning the plugs / fitting new spark plugs if you havent tried that already

You could also check / remove the air filter and see what its like with that, or run it with no filter / no airbox lid on just to see if it idles any better like that.

Did you drain the carbs of fuel before you stored it up for the winter, again when unleaded goes off it can leave a gummy residue on the carbs internals ( float bowls, jets etc etc ) so that might be also causing you problems.

Start with the basics first i.e. Fuel, Air, Plugs, Spark and take it from there before you start taking the carbs apart IMHO.