Alright i bought this quad a week ago....99' 400ex, and the valves were tapping from the getgo. It has a stage one hot cam in it. From what im told cammed 400s are supposed to tap? Went for a little rip yesterday and all of a sudden they started tapping LOUD and the exhaust seemed to be louder. All ehaust pipes are bolted tight. Shut it off immediatly. The dude i bought it from said theres no plunger valve or whatever in it. What do i do? Still has compression and fires right up.