Can the KIPS powervalve cause a loud clattering noise if it is not right or broken? I have a 1998 kdx200 that makes a lot of noise at lower rpms, goes away completely as it revs up. a shop said the rod and main bearings are fine. I checked the clutch assembly, it is fine. the nut on the magneto flywheel is fully torqued as is the nut on the primary drive gear. I am not familiar with this powervalve stuff. I am stumped.
If the "wave washer" is worn out or broken then it can allow the middle "valve" to clang around at low rpm's. Check that and also that the two side aluminum valves aren't broken.
this is not a rattle, more like a banging. I met 2 people I know who ride kdx's out in the dirt, and the noise mine makes is nothing like theirs. in fact they wouldn't ride with me, they were sure my kdx is about to blow up or seize or something. I may chicken out and take it to the kaw shop.
You should be able to remove the pipe and the little KIPS actuator lever cover and then look into the exhaust port with a flashlight. You can then move the KIPS rod in and out and see the center valve raise and the side valves rotate open and closed.