08 yz450f stock exhaust on 06 yz450f??

11 replies to this topic
  • ancona1

Posted April 16, 2009 - 05:58 PM


I have a stock 06 yz 450f and I put on a 2008 stock exhaust and I'm wondering what jetting I should have. Should it be jetted at the stock 08 settings??

I'm in so cal,
at about sea level
and its about 80 degrees out.

Any Input is greatly appreciated.


  • grayracer513

Posted April 16, 2009 - 06:17 PM


No hints for you. Start with what you had.

That pipe kills the mid range on an '08, and guys fix that by putting almost anything else on it. Let us know how it works out.

  • husqy360

Posted April 16, 2009 - 06:47 PM


i trayed an 08 this weekend with stock and then drd ti pipe.

first: my 06 killed both :p, second the stock pipe is for girls :lol:

  • ancona1

Posted April 16, 2009 - 08:22 PM


well the pipe was given to me, so should i keep the stock header and just put a slip on on? Is it just the muffler thats bad or the header to?

  • grayracer513

Posted April 16, 2009 - 08:41 PM


The header is an unusually large diameter to work with the muffler. If the pipe was free, try it if you want. Don't be too surprised if you don't like it, though.

  • 08YZ450Derek

Posted April 17, 2009 - 06:07 AM


I don't see the downfall of using the stock 08 header with a slip on. They connect, and the bike runs good. What would the benefit be from a different header? I mean, they sell slip on's for bikes that use the stock headers, hence slip on. I am wondering this, because I run the stock header setup and slip on. Has anyone on TT compared running a stock header and then the aftermarket header that compliments the slip on? Would it wake up the bike more? I would like to know. Thanks, Derek.

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  • grayracer513

Posted April 17, 2009 - 06:26 AM


The '08 header is larger to help compensate for the poor performance of the muffler. Examining any good complete system will reveal that none of them, including any of the OEM Yamaha systems, use a header as large as that. The reason is that with a fairly normal, freer flowing muffler, a header with too much diameter reduces the velocity of the exhaust gases leaving the engine to the point where the harmonics of the pipe no longer work correctly, and power is lost, rather than gained by it.

Slip-ons made made primarily to be sold, and it would defeat the concept of it being a slip-on if it were not able to be used on the OEM header. Using a slip-on on an '08 with the big header is still an improvement because the OEM muffler is such a complete dud, but you'd likely be better off by using a stock '06 header and a slip-on for that bike.

  • jjj109

Posted April 17, 2009 - 07:15 AM


My buddy just put a 08 complete exhaust on his 06 yz450f. It def reduce some power:foul: . The thing is we both ride where noise is a big issue. you def need to rejet when you put that pipe on. Also keep is mind the besides the jetting the ignition timing is different on the 2008 yz450f for that shorty pipe. So it might not run the best on an 06 450f. But it is nice and quiet

  • 08YZ450Derek

Posted April 17, 2009 - 07:17 AM


Would it have to be strictly an 06 header, or could it be an 07 also. They do bolt up right? Usually I see 06-08 for exhausts for Yamaha. I found a header on Ebay, its a Delkavic or something like that. Looks okay, but I have never heard of that brand. I can't find a Yoshimura header alone for sale, they only sell the setup on the website, and Ebay is different every day. So is the best buy to get a 06 or 07 header from an online sale? Thanks, I just want to get the most out of an exhaust setup for a reasonable cost.

  • grayracer513

Posted April 17, 2009 - 07:50 AM


The headers for that year range all fit on the engine, but they tend to be made with a variety of outlet diameters, so while they fit the head, they may or may not fit any other muffler besides what they were made for.

When buying aftermarket headers, this becomes important, as they may only fit correctly with that same company's mid pipe. If you but a Yamaha header, you can then order a slip-on for the year of the header if you like, and that will work.

  • live4speed

Posted April 17, 2009 - 07:56 AM


isnt the 08 pipe super restrictive? im confused... my 06 ran like a champ with Eddies recommeded jetting and stock pipe (i believe it was a 180 main and 48 pilot...)

  • ancona1

Posted April 17, 2009 - 09:05 AM


well, Ive heard bad things about the performance of this exhaust I mainly just liked the shorty style muffler. So I think will put my 06 exhaust back on. Is there any brand out there that performs well and also comes in that shorty style?

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