Not that im any kind of mechanic either but to my knowledge something like that i think has to do with carbeuration. You need to have then cleaned and sync'd. If it hasnt had service in a while you might as well get the valves checked and adjusted if they think it needs it. But valves can be expensive so if its been a while since its had any major service then get a major service done to it which will include the valve job and such. One way to check if the carbs need work is to put your hand on the bars and rev it to each rpm range and feel the vibrations grow stronger. You'll notice vibrations strong around the range you mentioned and then smoother afterwards. A mechanic showed me this and then i had the carbs cleaned and sync'd as well as a valve job which didnt need to be done. Much smoother afterwards.