Cleaning the carbs by spraying the juice down the throat of the carbs is like saying you've done a full engine rebuild 'cos you changed the plugs.
Another thing is that some carb cleaners are so volatile that they may detonate if you spray whith the engine running. never do this, just to be on the safe side.
The carbs need to come off, and you need to get right in there to see what's going on.
If there's any shite then it'll be in the float bowls, which the carb cleaner would never even go near just sraying it in.
Pull of the bowls and remove all the jets. You'll have great fun trying to get to the powerjets. They're hidden under an aluminium screw. you'll need a perfect fitting screw driver and probably a couple of whacks with the hammer to get those puppies loose. Then you'll need a nice small screwy that sneaks in to get at the jet itself. Be careful 'cos they're made of cheese and easy to break.
If necessary, spend a couple of quid and buy some new tools for this job. It's not worth messing up because of old worn tools.
When you've got all the jets out inspect thoroughly and clean as necessary. I use a special carb cleaner in an ultrasonic thingy, but popping the jets in a glass of Coke overnight has a very similar effect. I'm just too impatient for that and seeing as the ultra sonic cleaner was a present I intend to use it!
If there's any stubborn stains then I've got an array of cocktail sticks, pipe cleaners, cotton buds and some not too savage metal polish to get things back to spec.
Sometimes I even have to resort to the trusty broken throttle cable to use as a pokey. Just unravel the ends and you can make yourself a selection of different size pokeys from the wire strands. A primitive method that's been working for me for years.
Cleanliness is next to Godliness. Isn't that the saying? And I expect that God's out there in the shed right now cleaning His NSR carbs!