I have a 98 Yz400f that I am having trouble with. I have noise coming from the left side of the motor believed to be the cam chain. I took the bike to a shop and they said (just by removing the valve cover and looking) that the timing chain was bad and that was causing the noise. I was then quoted approx. 200 to replace it. First is noise from the cam chain on this bike common? How can you tell if the chain is bad just by looking.....it appeared to be tight and showed little wear from what I could see? If the noise is not common how hard is the chain to change if I did it myself? The chain isn't that expensive but I wondered if it is best to just let them do it. Any ideas?