Repacking my YZ400F Muffler

5 replies to this topic
  • PatrickM

Posted May 25, 2007 - 03:38 PM


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.

  • 642MX

Posted May 25, 2007 - 03:45 PM


I repack mine once a year. The FMF 4 stroke packing (that comes in a roll) is very good stuff to use. The loose pink stuff FMF sells is about worthless IMO.

  • PatrickM

Posted May 25, 2007 - 06:18 PM



I was going to get FMF's high performance stuff (pink one) but my local motorcycle stop did not have it so I got the roll stuff.

I had another question about re-packing the muffler...

the directions call for a silicone sealer.... is that silicone sealer really needed??

Thanks again everybody!!!!!

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  • 642MX

Posted May 25, 2007 - 06:24 PM


Its a good idea to smear a little silicone on the inside of the canister to help it seal. I just use the black RTV thats available at any auto parts store. Be sure to wipe off the excess silicone when your done.

  • DRH

Posted May 25, 2007 - 06:36 PM


Had your bike loved it. It was the best bike I have ever owned. You must make sure that your exhaust system is free from any leaks. This makes a big difference in how the bike performs. Make sure that the head pipe is seated properly with no leaks, the mid pipe is famous for leakage even though you are sure it is tightened and last the muffler should be free from leaks as well. Use the silicon if if is needed.

  • stillsun

Posted May 25, 2007 - 07:31 PM


We use stainless steel packing in our bikes.... has worked great for much longer life than fiberglass.

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