Exhaust repacking questions YZ426F

Yes I searched..without success.................

Ok I have a 2002 YZ426F with a stock pipe, and a pro moto billet end cap/spark arrester that I run supermoto events with. 4 trackdays ago I was performing some regular maint,oil chang etc.... I noticed that the front of my muffler was loose and the rivets were also loose. I decided since I had never repacked the pipe might as well do it while I'm here.

OK took everything apart and found a mesh screen with what looked like steel wool under it and around the pipe core, also the normal fiber tpye packing material around the outside of the mesh screen. all of the outer material was pushed to the back 1/3rd of the pipe. I discarded all of this packing material. Went to my local dealer and bought some O'neal packing. I then wrapped the packing around the pipe core and re rivited the pipe.

Now 4 trackdays later.....I have zero packing material in my pipe?? Also all the front rivets are loose again??

Is this normal?

should I have kept the mesh screen/steelwool looking stuff?

Have I hurt my bike?

What should I do to fix this issue?

TIA:worthy: :worthy: :worthy:

Sorry for the long post.


Did you use 4-stroke packing? There's a difference.

Yes, you should have kept the wire mesh/steel wool. Try it again with some FMF stuff.

Crap! I knew I should have kept that mesh stuff.......off to the shop

Crap! I knew I should have kept that mesh stuff.......off to the shop

sounds like too much back pressure w/o the mesh insert caused the rivets to expand and loosen....I also wondered about this...

Here is a company that has some higher quality packing


Pipe manufacturers will tell you to repack every 15hrs....I find that I can go longer than this with proper care on the packing....namely keeping all moisture out of the end on the pipe. I buy the rubber corks from Home Depot/Lowes that fit snuggly on the end of the pipe...2-6 bucks. :thumbsup:

I went thru this a week ago. do a search and you'll find a hour's worth of posts on this. But, I saved my "mesh" and installed fresh 4 stroke packing and have 3 hours on it and I don't have any problems. Did you use the correct drill bit size when you drilled the rivets out? Maybe you drilled the hole one size larger than needed?

Also make sure you are using steel rivets. I used aluminum ones before and they only lasted 2 races.

Thanks for the comments, stopped by a local shop and got a quality 4 stroke repack kit even got more steel mesh stuff. Good tip on the rivets, I used aluminum last time.

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