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MxRider18

07 450f Head work done. What exhaust?

10 posts in this topic

I installed a new head recently that i had ported by a reputible motor builder. From what i read in the past the 07 yz450 apparently has the most beneficial stock exhaust. (ive pulled multiple holeshots on modded bikes) But my buddy tells me if i really want to utilized the head work i need an exhaust to help it breathe. Does anyone have any info where i should start?

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Well it depends on what your looking for, exhaust doesn't make that much of a difference. Unless your doing a power bomb which gives a bit more bottom end and takes away top end. I run a 08-09 YZ450 head pipe with a FMF rear section. That could also be accomplished by a 08-09 full pipe with the baffles pulled out and a pro Moto billet end cap on the rear.

If your really looking for more power you should look into running a Mototusnari YZ250 air intake boot. That's if it fits but we fit them on the WR's though it's a bit tight. It made a big difference on my WR450's.

Edited by stevethe

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The YZ intake boot is considerably different.  It already has a tuned intake bell built into it, and IMO, shouldn't be replaced.  

 

As far as exhausts go, one of the best overall values to be had is the DRD full stainless system.  Get it with the spark arrestor (removable) for an extra $15. 

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The YZ intake boot is considerably different. It already has a tuned intake bell built into it, and IMO, shouldn't be replaced.

As far as exhausts go, one of the best overall values to be had is the DRD full stainless system. Get it with the spark arrestor (removable) for an extra $15.

Almost sure it fits and it's 1 hp on a YZ250f. It's 1 1/2 toward 2 depending on the build on a built 450. Somehow Yamaha didn't do the greatest job on the air boot. Edited by stevethe

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I tried these on my WR450(s), which have the YZ carb, stock WR airbox and boot,  Stage 3 port and polish by ASR, YZ igniton curve (Dynatek) and '07 YZ ex cam:

 

FMF Q4 with YZ header

FMF powercore 4 with YZ header

Dubach Racing (long header version with NS4 muffler)

Duach Racing (short header version with NS4 muffler)

ProCircuit T5 with YZ header

 

Now granted, the WR motor has a substantial amount of additional rotating mass, has a different intake tuning, and revs much slower to begin with, but the power delivery of the Dubach Racing NS4 + longer header was by far the most linear power to the ground feeling, plus it allowed for much earlier shifting (short shifting)....and it's half the price of everything else.

...but it's not a 'track' pipe, as there is virtually no hit or over-rev with my set up.

Edited by KRANNIE

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I also have to disagree with the use of the '08-'09 YZ header.  It's oversized to compensate for the extra restrictive "shorty" muffler used on those year models.  On that bike, almost any slip-on will gain 5 HP in the lower mid range (none on top, necessarily), but substituting either and '06, or the stepped header from an '07 raises the entire curve even farther across the board.  The '08-'09 header is just too big.  

 

Bear in mind that when you start with a late WR head, you're looking at a significantly different intake port.  That has an effect. 

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The 08-09 YZ450 header is the same size that FMF uses minus the fooner bombs. So it is a direct fit into a FMF rear section. It is the pipe we use in all the WR's that power up the big power hills. The other pipes have been tried and sold including Pro circuit and Mr. Dr. D.

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The YZ intake boot is considerably different.  It already has a tuned intake bell built into it, and IMO, shouldn't be replaced.  

 

As far as exhausts go, one of the best overall values to be had is the DRD full stainless system.  Get it with the spark arrestor (removable) for an extra $15. 

Gray Racer, thank you for your input but why the stainless over the other materials, and most of all why the spark arrestor?

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The spark arrestor is required under the AMA desert racing rules, so I run one.  There is no detectable performance hit as a result of running it.

 

Stainless steel is tougher and less expensive than Ti or carbon (I will not ever own a carbon fiber muffler unless it comes with a bike I buy), and again, there's no performance disadvantage to it.  I doubt there's as much as a pound of difference in the weight. 

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Well it depends on what your looking for, exhaust doesn't make that much of a difference. Unless your doing a power bomb which gives a bit more bottom end and takes away top end. I run a 08-09 YZ450 head pipe with a FMF rear section. That could also be accomplished by a 08-09 full pipe with the baffles pulled out and a pro Moto billet end cap on the rear.

If your really looking for more power you should look into running a Mototusnari YZ250 air intake boot. That's if it fits but we fit them on the WR's though it's a bit tight. It made a big difference on my WR450's.

It does fit 07-11 wr450's-

I have one on my bike at the advice of a roadracer from smj that has a couple 60+ hp yz's

The guys screen name is iload2 i think.

He stated that he couldnt break 59 hp with the stock boot on his bikes- the moto tassinari boot got him into the 60's.

1216152143_zpsn0iw7dye.jpg

As for how much I gained with it- hard to say because i did a complete rebuild with cams,mixxer head porting, megabomb header, bored carb and a hi comp piston at the same time.

The bike is a power house now compared to what it was stock.

With just free mods, yz cams and a pro circuit slip on it made 49 hp- i have an appointment friday to have it dyno tuned and im curious to see where im at now.

It revs alot faster- im hitting the factory rev limiter alot because it pulls so much harder now, definantly gonna take some getting used to.

Edited by knuckleduster271
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