I just pruchased a 1999 YZ400F (about 2 months ago) and I am doing all the services before i start to ride it on a regular basis (one or twice a week). I was reading on this forum that I should be repakcing my muffler on a regular basis. How often should I be re-packing my muffler? I have an older FMF muffler, is the FMF 4 stroke repacking stuff ok to use on my muffler or is there better things to use?? Thanks for all of your help TTers!!!!! Patrick M.