i dont know, when it idles the chain make a clinking sound and i think thats normal isnt it?
That is normal centrifugal clutch noise.
Is this a new kart and first time driving it? If not, what was the old setup like? I think that your gear ratio is too high for that clutch to handle with those large rear tires. You need a larger rear sprocket (will require longer chain, too), or a torque converter, IMO.
The only problem that I see with attempting to install a larger rear sprocket is that metal sprocket protection guard will be in the way. You will have to either modify or eliminate it.