09 yz450f exhaust issues

5 replies to this topic
  • vet45

Posted March 25, 2010 - 06:53 PM


ive got a 4 month old, 09 yz450f (bought new), stock muffler packing burned out in less than one month, ive tried several good quality repack materials but packing completely burns out in 2-3 hours. jetting was stock, does not appear to be lean but i have just richened main jet from 160 to 165, in an effort to lower exhaust gases temperatures....anyone have this problem?

  • Family Man

Posted March 25, 2010 - 11:07 PM


Problem is, its the stock exhaust. Dump it, save it for resale/back up, and get an aftermarket exhaust.

  • vet45

Posted March 26, 2010 - 05:25 AM


thank you for your opinion, but im looking for an actual mechanical explanation....ive not read where others are having this problem.

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  • motoryan25

Posted March 26, 2010 - 06:49 AM


Just a thought here, maybe the mechanical baffles in the muffler blow out the packing faster. I know the YZ is the only bike that comes with the cones built into the muffler which I think directs the exhaust into the packing. Try looking up Bristol Core, I have heard good things about their packing kits.

  • grayracer513

Posted March 26, 2010 - 08:28 AM


The packing kit you use needs to have a steel mesh inner liner in it or you're wasting time and money. The DRD pro pack is made like this. The '08-'09 muffler blows packing out more rapidly for the reason the motoryan suggests; the baffling cones divert the exhaust into the packing more directly and forcefully, and it's just hard on things. "Less than a month" seems quick, though. BTW, a richer jet will not necessarily lower exhaust temps.

  • Adammoto

Posted March 26, 2010 - 09:29 AM


Weird. My stock exhast packing has lasted a long time.

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