horriable noise

ive got a 91 350 TRX..i heard a noise about a month ago when i was on a tour..it almost sounded as if my bike was gonna fetch right up..i replaced the bearings and seals in the front hoping this was the cause..nope..i heard the noise again last weekend..i figured i was walking this time,but it seemed to fall back in place and was good again..its as if the shaft is coming out of spot and grinding somewhere but it seems to right itself and run good after a bit..i dont like sound or feeling whatsoever..any thoughts?