'07 exhaust q's

16 replies to this topic
  • BigBelly

Posted April 29, 2009 - 12:52 PM


I've got an '07 WR 450, free mods done, grey wire cut, throttle stop and it's been jetted. I love my bike and think it runs exceptionally well.

I jumped on a buddy's '05 "other brand" 450 and was absolutely blown away with the power of his bike. He was also shocked at the lack of power on my bike as compared to his. Both bikes are stock with free mods done the only difference is that his had a Pro Circuit Ti4 pipe and header.

I know the exhaust argument has gone circles around here but will a pipe and header TRULY make that big of a difference? Anyone ever do a dyno comparison?


  • zorroz

Posted April 29, 2009 - 02:08 PM


Pipes do make a big difference. I ran the stock pipe gutted with gytr baffle for a while but rode a mates bike with a pipe and went so much better that I ended up getting one myself. But then again 2008 Australian enduro champ Chris Hollis won on a stock WR450 cleaning up all the factroy bikes and his bike sounded very quiet at full noise.


Posted April 30, 2009 - 11:11 AM


I won my class championship with free mods and the GYTR end cap on my stock header and pipe... This was in GP and tight woods racing.

I'm not saying that more free flowing exhaust won't give you more but I found I never really needed it and $45 US and a few minutes of labor gave me enough flow while staying below our 98db noise rule:thumbsup:

Having said this... I just fitted a FMF Q2 and Mega Bomb header all mfg'd for an 06' YZ450F... I have not had a chance to even fire it up yet but I am expecting power gains...

  • Strattos

Posted April 30, 2009 - 12:06 PM


Re Chris Hollis winning the Australian Enduro championship last year, he actually fitted an aftermarket pipe but said he preferred the smoother power delivery of the stocker and he was quicker with it, and put the stocker back on.

For me, I know with my ability i'm never going to be able to extract everything that my '08 WR450's got, but riding is also about enjoyment. If I'm having more fun with more power than I need it's money well spent for me;)

I've got an FMF 4.1 on mine and absolutely love it. And in relation to other bikes, I never seem to be short on power with the group I normally ride with, which is a mix of CRFs and EXCs, and that's in sandy, whooped out riding which is pretty open and power-reliant in places. WRs still rock me for me and, the way I'm thinking at the moment having already owned two of them, I'll only be buying WRs in the future unless something radical comes along.

  • BigBelly

Posted April 30, 2009 - 01:34 PM


I just did a little reasearch and I think one of the differences is the stock gearng. Mine is 13:50 and the other bike (I think) runs a stock ratio of 13:51.

I know one tooth on the rear is no big deal by itself but that mixed with a pipe/header combo might be part of it, huh?

I would think dropping one tooth on the front would make a huge difference but not on the rear...any thoughts?


Posted April 30, 2009 - 01:50 PM


I used to always drop a tooth on the front with my WR's as most of my riding is tight technical stuff (pre 07' they came with 14/50).... so when I got my 07' I went out and got a 12T C/S sprocket and it was WAY TOO LOW for my taste... I have been happy with the 13/50 combo for the most part.

A 51T rear might workout alright:ride:

  • JSanfilippo

Posted April 30, 2009 - 09:35 PM


Hey BB if the other 450 was a honda it'll feel snappier no matter what because of the closer ratio gearbox. I read somewhere the gear spread on the 450x was closer to the '96-'01 CR 250 than it was to a proper wide ratio 5 speed.

  • BigBelly

Posted May 01, 2009 - 12:43 PM


I was trying to avoid the "my Red bike is better than your Blue bike" deal but yes, it is an '05 CRF 450X. You brought up a great point though, I had never thought about internal gearing. Everything else I've read shows that bike to have 13:51 (sprokets) but like I said, I can't imagine a single tooth (up) in the rear making that much of a difference.

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  • tunefx

Posted May 01, 2009 - 07:15 PM


I went to a 51 rear on my '07 this season. I noticed an immediate difference.

You didn't mention airbox mod. I would suggest doing that immediately. Followed by adding a pipe. Opening up the "inhale" is best matched by opening up the "exhale." All this resulting in needing a JD jetting kit or the GYTR AIS removal kit (comes with jets/needles).

Do the above and you will find yourself taming a wild new animal. And, IMHO, you will have your red friend looking at ways to mod his bike after riding yours again.

  • desdave

Posted May 02, 2009 - 03:35 AM


I did all the free mods, including modifying the stock exhaust on my 08 wr450. I then added an fmf Q4, and was surprised how much it increased the overall power. Really really woke it up. I then added a power bomb header, but can't honestly say I felt any additional change with that addition.

  • WR450FGreg

Posted May 02, 2009 - 02:09 PM



modifying the stock exhaust on my 08 wr450.

This needs to be done properly, not half-assed (I'm not suggesting you in particular did it this way desdave BTW! It's just that it seems that so many do.)

It needs to be modified right through in order to achieve real gains in performance.
Investigate not only what you can see from the outside, but also the "guts" of your muffler, then do the math (calculate effective oriface diameters etc.)..... then modify properly and HANG ON!

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  • Swiveler1973

Posted May 02, 2009 - 05:35 PM


I have a 07 wr450f, I just put on a 2008 yy450f shorty pipe for 50 bucks that I got off of ebay. More power. less weight, low in cost. I am happy with the resulsts.

  • mikeythefokker

Posted May 04, 2009 - 10:32 PM


Pipes really do make a tremendous difference. I wish that they didn't because they sure aren't cheap. The stock yz exhaust when fitted with a pro moto billet sparky is a pretty decent setup, but I don't know how one would do in the db department.

  • bwardipi

Posted May 05, 2009 - 02:56 AM


i think these WR450s are delivered completely different in every country, so i am speaking from Australia. If i'd ridden a stock bike for a test drive i would never have bought one. The way i picked up my 08 was rubbish. It was boggy, restricted and slow. My mate commented that he thought my postie bike was faster (Honda CT 110 down here) and he was probably right. There is no way Chris Hollis or anyone else rode a race with one of these things stock. I removed everything 1-by-1 assessing each performance change. Removing airbox rubbish was the single biggest improvement, giving the engine the hope at life it deserved, only to be choked by that life sucking muffler. Stuck on a Aluminium Pro II muffler and it really came to life.

It seriously is bullshit that you make a $12,000 performance race bike and deliver it in that state. Regulations or not, you can make a fast bike and still
meet the regulations. I don't stand for that excuse. I have a 2.3 litre, 204kw car that meets all the regulations and still gets 5.6 litres/100km on the open highway. I also have an sv650 road bike that pumps 72 bhp and also meets all emissions and noise standards.

  • WR450FGreg

Posted May 06, 2009 - 02:37 AM



The way i picked up my 08 was rubbish. It was boggy, restricted and slow.

Mate, sounds like you picked the wrong dealer!
Dave Fraser (near Wollongong) sold me mine totally unrestricted, it flew from the first ride.


  • bwardipi

Posted May 06, 2009 - 11:54 PM


there is no doubt it was the wrong dealer. good price, but NO product knowledge. Couldn't tell me what the main jet size was, even after they had replaced it with the one from the "spares" kit. "oh, we just put the one in from the kit". who does that??? without knowing what they're actually doing. As it turns out, the bike is so rich the spark plug looks like chargrilled bacon. It was also delivered with a dodgy mirror, and when i complained they said "everyone just pulls them off anyway". Well i'm not everyone, i like my mirrors and have always had them on my dirt bikes... it's a necessity when everyone else is always behind you!! HAHA. getting off thread. Yes, exhaust is a must, that with adequate air intake.

  • WR450FGreg

Posted May 07, 2009 - 03:13 AM



As it turns out, the bike is so rich the spark plug looks like chargrilled bacon.

Aaah, actually I must admit that mine was quite rich when delivered too come to think of it.
It certainly still went well initially, but even better soon after that first ride after I'd gone down a couple of sizes in main jet.



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