2008 WR450F with 2006 YZ suspension and cams


219 replies to this topic
  • kawi380

Posted July 03, 2013 - 05:34 AM


Learned something new today:

The WR's have 35mm un-tapered headers
The YZ's have 42-45mm tapered headers and exhaust
The back-pressure drop on the YZ pipe is designed to mate with the higher flowing YZ head
Other wise, the power band will shift to higher rpms.

So, I am going back to the stock WR header and a highly modified stock pipe, to get my bottom end back.


When I changed from a full wr system to a full 09yz system (the super short can) I noticed only a slight shift up (very minor) and lots more noise. the yz system is way too loud :naughty: So now I have the pmb end cap with a quiet core and it seems to be lots better and powerwise pretty similar to the stock setup.

  • grayracer513

Posted July 03, 2013 - 06:56 AM


There are a minimum of 4 different YZ450F headers available (Gen1 and Gen2); the '03-'05 (Gen1), the '06, the '07, and the '08-'09 (all Gen2).

The '03-'05 was a straight diameter, and can directly replace the the '06 on a YZ, even though the outlet angle is slightly different.

The '06 header is also a straight 40mm (ID) pipe. Measuring a used one often shows the outlet closer to 39mm.

The '07 used a stepped header (not tapered), smaller at the entrance, but larger at the outlet than the '06.

The '08-'09 header was larger yet, but not to match the "higher flowing" YZ head. In fact, it's a compensation for the ridiculously restrictive internal design of the cute little "shorty" muffler they came with. The '08-'09 YZ450F exhaust system verifiably cuts between 5-7hp at 5000 RPM, the heart of the lower mid range.

From a performance standpoint, the '08-'09 setup was clearly the worst by a considerable margin, and doing almost anything that replaced the muffler added an immediately significant gain in the mid range. But the oversized header is not the way to go if using an aftermarket muffler to improve power, as it interferes with exhaust efficiency at higher speeds. The '06 or '07 headers are a far better choice.

OTOH, if using a more restrictive muffler, inserts, etc., to achieve a quieter exhaust, the '08-'09 header could be the ticket.

  • kawi380

Posted July 03, 2013 - 07:32 AM


The '08-'09 header was larger yet, but not to match the "higher flowing" YZ head. In fact, it's a compensation for the ridiculously restrictive internal design of the cute little "shorty" muffler they came with. The '08-'09 YZ450F exhaust system verifiably cuts between 5-7hp at 5000 RPM, the heart of the lower mid range.

From a performance standpoint, the '08-'09 setup was clearly the worst by a considerable margin, and doing almost anything that replaced the muffler added an immediately significant gain in the mid range. But the oversized header is not the way to go if using an aftermarket muffler to improve power, as it interferes with exhaust efficiency at higher speeds. The '06 or '07 headers are a far better choice.

OTOH, if using a more restrictive muffler, inserts, etc., to achieve a quieter exhaust, the '08-'09 header could be the ticket.


Wow the change from 08wr to 09yz system didn't feel like 5-7 ponies :jawdrop: but then I did the end cap and quiet insert at the same time so I never used the stock yz system (started it and road it around the block but it was way too loud so straightway installed the quiet stuff). :thumbsup: Plus I like the 'cute' shortie silencer. :awww:

Edited by kawi380, July 03, 2013 - 07:33 AM.


  • beezer

Posted July 03, 2013 - 07:36 AM


The steel framed WR's came with the bigger diameter header pipe.

The aluminum WR's came with a smaller diameter than the YZ.

I put a DR. D YZ pipe on before I even rode the bike.

I doubt the bigger header is causing the loss of bottom end.

I think the difference between the YZ and WR heads is some emission fittings. I'm pretty sure they flow the same.

  • grayracer513

Posted July 03, 2013 - 10:22 AM


Wow the change from 08wr to 09yz system didn't feel like 5-7 ponies :jawdrop:


To be clear, while the '08-'09 system wasn't the best for top end, it did not cost the bike much at peak power (8700 RPM) when compared to other exhaust setups. The dip was between 4000 and 6000. Just a slip-on would get rid of it.

Again, that info is pertinent to "race" exhausts, and may not directly apply with quieter models.

  • Krannie McKranface

Posted July 03, 2013 - 10:44 AM


I have a Dubach Racing '07 YZ full system now. It's too loud, and too peaky.
I went with the Dr D because on my Hondas they work fantastically.

Not so much here....

  • 1abv

Posted July 03, 2013 - 12:10 PM


Intresting... I bought my bike w the GTYR insert and it had a YZ header not sure what one. hmmm maybe going back to stock is the ticket....

  • n16ht5

Posted July 08, 2013 - 06:53 AM


I have a Dubach Racing '07 YZ full system now. It's too loud, and too peaky.
I went with the Dr D because on my Hondas they work fantastically.

Not so much here....


bummer. is that with the quiet insert?

  • gcally

Posted July 08, 2013 - 09:53 AM


I have a Dubach Racing '07 YZ full system now. It's too loud, and too peaky.
I went with the Dr D because on my Hondas they work fantastically.

Not so much here....


I still think you should bite the bullet and try putting the stock cams back in.

Dr D list’s the same part number for WR and YZ full exhaust. They said their YZ/WR header starts out at 38mm and tapers to 41mm. They also said that their YZ/WR pipe should not rob any power from low end. From reading the forums a lot of people have put YZ OEM and aftermarket exhaust on the WR. Most have said that low/mid was the same put more power up top from the YZ exhaust. I think the cams are the problem with your power curve.

I will have to measure my full Akrapovic YZ exhaust when I get home to see what size the header pipe is.

Also I have a brand new Stock WR system I was going to put on eBay this week. It already has the Yamaha open end cap for the WR.

  • gcally

Posted July 08, 2013 - 09:58 AM


I also checked out FMF header pipes and they use the same part number for YZ/WR.

MegaBombfor 2007 YAMAHA WR450F Item ID: 044227
MegaBombfor 2009 YAMAHA YZ450F Item ID: 044227

MegaBombfor 2007 YAMAHA WR450F Item ID: 044353
MegaBombfor 2009 YAMAHA YZ450F Item ID: 044353

PowerBombfor 2007 YAMAHA WR450F Item ID: 044225
PowerBombfor 2009 YAMAHA YZ450F Item ID: 044225

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  • Krannie McKranface

Posted July 08, 2013 - 12:37 PM


I also checked out FMF header pipes and they use the same part number for YZ/WR.

MegaBombfor 2007 YAMAHA WR450F Item ID: 044227
MegaBombfor 2009 YAMAHA YZ450F Item ID: 044227

MegaBombfor 2007 YAMAHA WR450F Item ID: 044353
MegaBombfor 2009 YAMAHA YZ450F Item ID: 044353

PowerBombfor 2007 YAMAHA WR450F Item ID: 044225
PowerBombfor 2009 YAMAHA YZ450F Item ID: 044225


Yeah, I know. The pipe that came on the bike was and FMF 'for a WR' but it had the larger header.

Edited by Krannie, July 08, 2013 - 12:38 PM.


  • KennyMc

Posted July 08, 2013 - 01:08 PM


[color=#ff0000]I still think you should bite the bullet and try putting the stock cams back in.[/color]

Dr D list’s the same part number for WR and YZ full exhaust. They said their YZ/WR header starts out at 38mm and tapers to 41mm. They also said that their YZ/WR pipe should not rob any power from low end. From reading the forums a lot of people have put YZ OEM and aftermarket exhaust on the WR. Most have said that low/mid was the same put more power up top from the YZ exhaust. I think the cams are the problem with your power curve.

I will have to measure my full Akrapovic YZ exhaust when I get home to see what size the header pipe is.

Also I have a brand new Stock WR system I was going to put on eBay this week. It already has the Yamaha open end cap for the WR.


The thing is he and I have the same cams in and he rode his bike around the street and then rode my bike. Said could tell the difference between the 2 bikes then. :excuseme: I do have a light port job on my head though...

  • Parx_400

Posted July 08, 2013 - 01:09 PM


I have a Dubach Racing '07 YZ full system now. It's too loud, and too peaky.
I went with the Dr D because on my Hondas they work fantastically.

Not so much here....


Might be the newer style pipe. I had the older (Not super older) style DRD on my last wr450. It was amazing right off bottom. This was an 05. It was pretty damn loud though.

  • gcally

Posted July 08, 2013 - 05:13 PM


Learned something new today:

The WR's have 35mm un-tapered headers


I just measured my stock 07 WR header 38 mm un-tapered.

Edited by gcally, July 08, 2013 - 05:19 PM.


  • gcally

Posted July 08, 2013 - 05:18 PM


My YZ Akrapovic header is 40mm most of the way then tapers all the way up to 45mm a couple of inches from pipe connection.

Edited by gcally, July 08, 2013 - 05:19 PM.


  • Krannie McKranface

Posted July 08, 2013 - 05:23 PM


Might be the newer style pipe. I had the older (Not super older) style DRD on my last wr450. It was amazing right off bottom. This was an 05. It was pretty damn loud though.


Yes the older pre 2007 DRD pipes were 35-38mm headers all the way back to the muffler. Had one on my '03. It was a torque monster.

  • Krannie McKranface

Posted July 08, 2013 - 05:27 PM


I've been reading up on the mapping options available with the Dynatex FS device.
It seems you have (3) distinct map options for each 'number' option, with 'turn-points that allow you to do the map switching by design within one map.
The #3 map is the most aggressive off idle, and stays in that map all the way to 40% throttle, where it goes even more aggressive
The other 4 maps all swtich from 0 throttle tps to 25% throttle TPS, to 40%+ throttle tps, hence the still presence of the stutter.

I will learn more and post results.

The new needle came, but I don't have time to put it in. it's the richest FCR CR needle I could find.....

  • stevethe

Posted July 08, 2013 - 05:58 PM


Well everyone's got an opinion especially on pipes. I've owned many WR's with many pipes for a very long time and have not had enough of a difference to bring you what I believe your missing. Don't think it's the cam either. Do some research on this http://www.factorypr...mu_hi_disp.html the reason they are torque-less wonders stock.

Edited by stevethe, July 08, 2013 - 06:04 PM.


  • Krannie McKranface

Posted July 08, 2013 - 06:30 PM


Well everyone's got an opinion especially on pipes. I've owned many WR's with many pipes for a very long time and have not had enough of a difference to bring you what I believe your missing. Don't think it's the cam either. Do some research on this http://www.factorypr...mu_hi_disp.html the reason they are torque-less wonders stock.


Yeah, I had that tube on my first '07. I have one for the present bike, but have not put it on.
I plan on doing the tube and the needle this week.

The only problem with that logic is that every other FCR bike I have owned (accept KTM's) have zero flat spot even with the standard needle jet emulsion tube.

Edited by Krannie, July 08, 2013 - 06:31 PM.


  • shrubitup

Posted July 08, 2013 - 06:49 PM


just picked up a mint '09 YZ450F. Not messing with stock motor or exhaust (other than PMB end cap). Perfect for slow single track. Hot start with one kick and no hot start lever used. :awww: :worthy: Will mod the suspension. Watching your thread. :thinking:




 
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