Excessive carbon on spark plugs

Several things come to mind on this. First, rejetting should be done by someone that can do all of the fine tuning also. If the idle mixture screw on the carburetors are still covered, you need to expose them for adjusting. Pull one spark plug and look at the color of the electrode. Black is too rich (too much gas) and white is too lean. You want a lighter brown. Put the plug back in and start the bike. On each cylinder, adjust that idle mixture screw all the way in, being gentle, to the stop. DO NOT OVER TORQUE, YOU JUST WANT TO REACH BOTTOM. Make note of the screw driver orientation and back the screw out 2 turns. This is the starting point. If the bike will no longer idle, adjust the idle screw for about 1000 rpm's. After running the engine for a couple of minutes at idle, do not rev the engine, just shut it off. Pull a spark plug and check the color. Again, you are looking for a light brown. If it is black, turn that carbs mixture screw in 1/2 turn, white, turn out 1/2 turn. Do this for each carb. I know, this is not the quickest way, but it is a sure way of getting the right mixture. It will be time consuming and you might even burn your fingers on the hot plugs.
Now that you have the right mixture, it is time to balance the carbs. I use a Carbtune monometer. Google Carbtune. This is a must to get the bike to run strong and smooth. You will need a service manual for this procedure. Go to Delphi Forums and look up the RSV, Royal Star Venture forum and you will find an electronic version of the service manual there, for free. Hope this helps.
btw, there is not anything around the spark plugs to adjust.

U need to adjust the tunning of ur bike .. jus ask the mechanic to adjust the the bolt and nut under ur bike's head .. jus above the spark plug .. this wil surely improve ur bike's performance ..