Tri-lite

My max is making a wierd kind of clicking sound... at first it would only do it on first then it worked its way up to second and third... one of my buddys things it might be the valves but he says it's to much of a deep sound for it to be the valves... anyways im going to bring it in next week to get it checked I was just wondering if anybody ever experienced anything like this ... and I was wondering if anyone knew what this sound is and if it costs alot to repare ....

thanx ..