07-09 YZ450F exhaust?

[lumpy790]

I recently picked up a bone stock 08 YZ450F and a friend was telling me how choked up the muffler is stock and that there were different header diameters from 07-09.

Any one know what the differences are between the years?

I have a line a used Yoshimura slip on locally and I want to make sure the header will work or possibly pick up a larger diameter header.

[Steel Panther]

The stock 08-09 silencer is restrictive, they made the header diameter larger to try to account for it. A slip on will help but a full system is much better. Its important to realize bigger is not always better for exhaust flow, you want a balance between a small diameter, which moves air out fast, and a large diameter that lets enough air out.

[lumpy790]

Interesting. I thought it would be the other way around since the 08/09 450 uses the same header (part number) as the 250.

[KJ790]

Interesting. I thought it would be the other way around since the 08/09 450 uses the same header (part number) as the 250.

I don't know where you heard that, it is not true. You can't swap the 250 and 450 headers, they won't even mount in the head. Like stated, the 08-09 YZ450F header was made larger than previous years to try to account for the restrictive silencer. When a better silencer is put on with the stock header, that header is often too large. I would suggest getting either a full system, or using an earlier stock header with a good slip on. The 03-06 headers are the same, 07 was slightly larger at the midpipe joint, and had a slightly different bend to account for the engine being angled a couple degrees. 08-09 are even larger than the 07. You can get the 03-06 header to fit fine, but you will need a slip on that will fit that header (one that lists fitting the 06 YZ450F in that case). If you get an 07 header then obviously you will need a slip on that fits the 07 YZ450F to match the pipe diameter. Some companies like FMF use a very large midpipe and supply different sized sleeves to match the different headers so that one slip on will fit 06-09.

[lumpy790]

If you do a reverse look up with the OEM Yamaha part number 2S2-14611-30-00 it is the same header for both the 2008 250 and the 2008/2009 450

So a slip on with the higher flowing 08/09 header is bad? Why?

[grayracer513]

The parts book does call for the same header, but the '08 250F looks to have the same lame muffler as the '08 450, so that may be why.

Incidentally, the '06 header is not the same as the '03-'05 (2S2...00 vs. 5TA...00), but the outlet diameters are the same, and people report being able to use one in place of the other. The '03-'05 cylinder tilts forward at about 5 degrees, whereas the '06-'09 was straight upright. The '07 used a header with multiple steps in it and the larger outlet KJ mentioned.

The '08-'09 header was oversized to compensate for the restrictive muffler, and is too large for good performance with any sort of free flowing silencer in place. The gas velocities are too low with the big pipe. A better muffler is an improvement, but better still is a full system, or a slip-on with an earlier header, as he mentioned.

[dvn]

the '08 250F looks to have the same lame muffler as the '08 450, so that may be why. QUOTE]

The 250 does not have the same muffler as the 450. The only models that the shorty muffler came on are the 08 and 09 450.

[lumpy790]

OK let me back up a little here. I am more of a bottom/Mid with a little top end rider. Without getting a full blown big $$ system What will best suit my needs?

[KJ790]

Here's part numbers:

03-05 YZ450F header: 5TA-14611-00-00

06 YZ450F header: 2S2-14611-00-00

08 YZ450F header: 2S2-14611-30-00

08 YZ250F header: 5XC-14611-20-00

The 250F and 450F headers cannot be interchanged, they are a different size at the head.

I think the cheapest route for you would be to try to get a full 06 or full 07 stock system, or get a stock 03-05 or 06 header with a good performing slip on. The large 08 headpipe hurts exhaust velocity and thus hurts low end power when paired with a good flowing silencer.

[grayracer513]

Here's part numbers:

03-05 YZ450F header: 5TA-14611-00-00

06 YZ450F header: 2S2-14611-00-00

08 YZ450F header: 2S2-14611-30-00

08 YZ250F header: 5XC-14611-20-00

The 250F and 450F headers cannot be interchanged, they are a different size at the head.

Interesting. Using the Yamaha online parts book as a source ( http://www.yamaha-motor.com/sport/parts/home.aspx ), there is an error in the model listings that lead me to the 2S2-14611-30-00. The models list includes two entries for "YZ250F - YZ450FX*". Obviously wrong, but I didn't notice it. The two models are listed separately in the list, and the 250F has the 5XC..20 listed there.

Incidentally, the '07 450 uses a 2S2-14611-20-00 header.

[lumpy790]

Thanks for all of the info guys. ?

My guess is Yamaha superseded a part number. If you do a reverse look up threw Yamahas system the 08 250F shows the same header part number.

[KJ790]

Thanks for all of the info guys. ?

My guess is Yamaha superseded a part number. If you do a reverse look up threw Yamahas system the 08 250F shows the same header part number.

Yeah, that must be a mistake on their part, as if you look up the 08 YZ250F it shows a different part number, and having both bikes I can tell you that the headers are completely different.

[grayracer513]

Thanks for all of the info guys. ?

My guess is Yamaha superseded a part number. If you do a reverse look up threw Yamahas system the 08 250F shows the same header part number.

It wouldn't be a matter of superseding the number, because the 250F has never used the same header as a 450 or 426. The reverse lookup SNAFU more likely relates to the double/crossed listing of the two bikes that I mentioned.