which YZ exhaust cams work in POST(!) 2012 WR450F

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51 replies to this topic
  • stevethe

Posted June 04, 2015 - 02:47 PM

#21

Jesus you are mixing up years, models, types, cams, heads, ignition timing, pipes, and putting it all on the responsibiltiy of a cam change between models that are not even compatable.
 
 
Good 
 
Luck 
 
With
 
That


Took the words right out my mouth. I feel sorry for someone doing a search of YZ cams in a WR.

Comparing a bag of potato chips to cole slaw back to an apple.

Hum is this the reincarnation of guy that took the starter out of 2012 model to lighten it up a bit.

  • Krannie McKranface

Posted June 04, 2015 - 02:59 PM

#22


Hum is this the reincarnation of guy that took the starter out of 2012 model to lighten it up a bit.

 

I don't think so. Still drinking gasoline though......



  • WRF-Rowdy

Posted June 04, 2015 - 10:01 PM

#23

Jesus you are mixing up years, models, types, cams, heads, ignition timing, pipes, and putting it all on the responsibiltiy of a cam change between models that are not even compatable.

Actually no. I was merely demonstrating what the 400's recation to cam retarding was.

At least on the '98 opeing the airbox mod did not much compared to +10% hp the cam retarding was yielding.

 

I found it interesting that yamaha's advancing the cam killed approximately the same amount of hp,

that adding the 50cc displacement of the 450  (with wr timing) has given us, meaning

above 7000 rpms : WR400F-YZ = WR450F-WR hp-wise

 

Just to counter the myth that "playing with cam timing" won't yield noticable hp. 

At least for the old 400 retarding the cam was THE TICKET to more hp,

free of charge and still not falling apart in 20.000 miles (at least thats when i sold mine)

 

But maybe you are right and with the '12 I won't see these effects anymore, time and dyno will tell.


Edited by WRF-Rowdy, June 04, 2015 - 10:39 PM.


  • WRF-Rowdy

Posted June 04, 2015 - 10:34 PM

#24

GYTR cams for the WR will drop in and work if you want to pay.  Or experiment with another cam and reshaping decomp pins.

I got no experience with that.  Nobody on the forums is going to help you.

That is the dissapointing part. The original DIY spirit of the pre '06 years appears to be gone.

Today everyone seems to ship his head or cams to and fro some shop to have them do the magic.

Basically a good sign, a wealthy society.  But I still like unconvering the free hop ups that yamaha

and the DMV have buried.

But of course, maybe there are no free tweaks in EFI WRs anymore, and I'm chasing a unicorn...



  • WRF-Rowdy

Posted June 05, 2015 - 03:40 AM

#25

I suspect the mega bomb took some power off the top.

Speaking of,  What, in fact, is the rational behind putting these mega/power-bomb chambers into the header pipe?



  • stevethe

Posted June 05, 2015 - 05:16 AM

#26

That is the dissapointing part. The original DIY spirit of the pre '06 years appears to be gone.

Today everyone seems to ship his head or cams to and fro some shop to have them do the magic.

Basically a good sign, a wealthy society.  But I still like unconvering the free hop ups that yamaha

and the DMV have buried.

But of course, maybe there are no free tweaks in EFI WRs anymore, and I'm chasing a unicorn...

 

So yeah the 07 + WR450's no longer have a HP-less cam from Yamaha. The cam is the same as the current F.I. WR450. The cam simply comes on differently than the GYTR and YZ the GYTR provides a little more over rev. However it is still a MX dirt bike cam.

Your stock motor corked up provides very little HP just as the carbed version. You will likely end up with a big power difference uncorking, GYTR ECU, open air box, PC Racing air filter, cut out the back fire screen and work out a free flowing pipe.

They usually go from anywhere around 42 RWHP to 48 + RWHP. Depending on the Dyno as your results will vary and may vary with FI.

 

Speaking of,  What, in fact, is the rational behind putting these mega/power-bomb chambers into the header pipe?

Quieter and more bottom end power. The mega bomb will sacrifice top end performance at the sake of low end performance. I bought one years ago and the bike would not climb the monster hills where we ride. I sold it to my bother that lives and does a lot of riding in Baja and he loved it. Go figure different strokes for different folks. Real top end HP pipes don't appear to use any bombs. I use a 08-09 YZ450 Ti header with a open style 4.1 FMF muffler. The 08-09 YZ450 muffler with all the baffles removed and a Pro moto billet end cap or any open muffler would work. However I don't know about fitment on the 12+.

You should Post up your before and after Dyno results if you can. Apparently at some point it is very hard to squeeze a HP on a Dyno. However to reasonable HP number it is just common sense.


Edited by stevethe, June 05, 2015 - 06:24 AM.


  • beezer

Posted June 05, 2015 - 09:07 AM

#27

Took the words right out my mouth. I feel sorry for someone doing a search of YZ cams in a WR.

Comparing a bag of potato chips to cole slaw back to an apple.

Hum is this the reincarnation of guy that took the starter out of 2012 model to lighten it up a bit.

 

 

I miss that guy.

 

He livened up the place.



  • grayracer513

Posted June 05, 2015 - 09:29 AM

#28

A whole lot of assumptions going around here.

 

You can say that again. 



  • chu

Posted June 05, 2015 - 02:30 PM

#29

So I don't know where you read, "that the cam from a carb'd yfz should work when it's retarded a tooth", but forget you read it.  It's wrong.

 

Edit:  In the case that you actually are talking about the cam from a Quad, and not just misusing the "YFZ" label as many do, there is very little difference between that and the original '03-'06 WR ex cam, but there again, retarding the cam one tooth will destroy your cranking compression unless you grind the decomp pin down.

 

You really think the cam from the quad wouldn't work retarded a tooth?  The difference between the 03-06 WR exhaust cam and the quad is in the decomp pin.  If it was a WR cam, you would have to grind the pin to lessen the decomp.  The quad cam retarded would actually have more cranking compression than stock because of the shorter pin.  Guy that degreed it said the exhaust valve would close 12 degrees earlier one tooth retarded.  Hate to bring it up again.



  • grayracer513

Posted June 05, 2015 - 02:49 PM

#30

12 degrees earlier than what?



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  • WRF-Rowdy

Posted June 05, 2015 - 11:59 PM

#31

So yeah the 07 + WR450's no longer have a HP-less cam from Yamaha. The cam is the same as the current F.I. WR450.

Maybe my wording was less than optimal: I never assumed that yamaha designed a different, an HP-less cam for the WRs.

Simply because of cost, they just took the YZ cam and changed one punch mark on it and used a slightly different decomp pin shape, nothing else.

 

As can be seen from my pics of the '12 WR exhaust cam vs. the '06 YZ ex. cam:

when they are aligned correctly not only the cam lobes but the whole decomp mechanism and the "12 'o clock punch mark"  are rotated.

 

It's really the sam cam, always has been. Rumor has it they changed the height of the lobes around '07,but I think

each year the WRs got the YZ cams with the 9 'o clock punch advandced one tooth and the e-start decomp pin.

They did not rotate the press fit sprocket, just the alignment punch mark, the other punch mark on "WR cams" still is where it is on the respective YZ cam.

Would make sense: you optimize the YZ year after year and mellow it down for the WRs at next to no cost by punch mark rotation.

 

 

cut out the back fire screen

Whasset? Do you mean the wire lattice trash bin shaped spark arrestor in the muffler or the lattice between air filter and intake ?


Edited by WRF-Rowdy, June 06, 2015 - 12:03 AM.


  • grayracer513

Posted June 06, 2015 - 06:54 AM

#32

Maybe my wording was less than optimal: I never assumed that yamaha designed a different, an HP-less cam for the WRs.

 

Oh, but they did.  From '98 through 2005, they did in fact use the same intake cam, and an exhaust cam with the sprocket indexed differently to reduce overlap.  However, with the '06 model, the WR got its own exhaust cam, followed in '07 by a more restricted intake cam.  They've been changed a couple of times after that, always in an effort to meet standards set by the EPA.  The reason you see the 12:00 marks "rotated" is because they were punched in a different spot relative to the timing mark.

 

Regarding the backfire screen, leave it in.  According to dyno tests done by Doug Henry's super moto team, there is no effect on power with or without it.  Air flow testing shows why: the filter is more restrictive than the screens are, so it makes no difference.



  • chu

Posted June 06, 2015 - 07:11 AM

#33

12 degrees earlier than what?

 

In this post http://www.thumperta...ween-wr-and-yz/

He put a degree wheel on a YZ, WR, and YFZ quad exhaust cam and measured what the decomp pins do.

YZ closed the exhaust valve at 26 degrees BTDC, lots of decomp for easy kicking

WR was 40 degrees BTDC, moderate decomp works better with the electric start

YFZ quad was 73 degrees BTDC, very little decomp, WR battery wouldn't be able to turn it.

YFZ cam retarded a tooth would close at 52 degrees BTDC.  12 degrees earlier than a stock WR,  Not my math, maybe it's like 50.5 degrees 10.5 earlier?

So the starter motor wouldn't spin so fast like with a YZ cam.  It would be a little less decomp than stock, but the battery might be able to crank it.



  • stevethe

Posted June 06, 2015 - 02:17 PM

#34

I see misinformation in your post that was quoted.

 

It says a YZ decompression pin and cam will work in a WR. Then why is everyone grinding the pin.

 

It says the 07' WR intake cam is unique to the 07 WR450. Then why is the part number the same till 2012.

 

Trust whom you wish in your quest to do whatever it is your trying to do.


Edited by stevethe, June 06, 2015 - 02:19 PM.


  • stevethe

Posted June 06, 2015 - 02:24 PM

#35

As far as air cleaner back fire screens and restrictive filters I find major power losses with them.

 

If you want to know what the Graves factory supported Yamaha Supermoto bikes look like. They do not restrict their air filters or air box's.c90c9d3f.jpg



  • grayracer513

Posted June 08, 2015 - 08:47 AM

#36

The info I'm referring to is dated, but inasmuch as the YZF filters and screens have remained identical from '98 through '09, I believe it's still valid.

 

Doug Henry's team was at that time working with an '03 YZ450, and tried 9 different air box configurations, with and without the screens, with and without other cutouts in the box itself, etc.  Not one showed any significant gain over the OEM setup beyond the selection of the best performing filter element.



  • stevethe

Posted June 08, 2015 - 06:55 PM

#37

I don't think everyone is going to get the same results as there are many different factors like which air filter you run. But I can tell you built 450 Yamaha's appear to want lots of air with no backfire screens all the way to almost no air box with a Hugh K&N or they are leaving power behind.

 

Here is a dyno test where a Yamaha WR250X street bike picked up over 2HP by opening the door to the filter. He was running a K&N. Note: I wouldn't run and don't like K&N's unless in a full out road race bike. http://www.wrrdualsp...esting/71-dyno2



  • grayracer513

Posted June 09, 2015 - 10:39 AM

#38

I Note: I wouldn't run and don't like K&N's unless in a full out road race bike.

 

Me either.  They actually do a really great job,... for a little while.   They just don't do it for long enough to be practical in "real dirt bike" environments.



  • RockerYZWR

Posted June 10, 2015 - 02:16 PM

#39

This cam swap discussion is more confusing than it needs to be.  Here are two questions I have (and I've read and researched everything I can about the subject on this forum), if someone wouldn't mind addressing them:

 

Is there anything to be gained by retarding the exhaust cam one tooth on the 07+ WR450F?

 

Can I simply install a 06-09 YZ450F exhaust cam (understanding that they're not all the same, would go with the 06 based purely on what I've read on here) with the decomp pin ground and polished approximately 1mm and still expect the electric start to work?



  • stevethe

Posted June 10, 2015 - 02:54 PM

#40

This cam swap discussion is more confusing than it needs to be.  Here are two questions I have (and I've read and researched everything I can about the subject on this forum), if someone wouldn't mind addressing them:
 
Is there anything to be gained by retarding the exhaust cam one tooth on the 07+ WR450F?
 
Can I simply install a 06-09 YZ450F exhaust cam (understanding that they're not all the same, would go with the 06 based purely on what I've read on here) with the decomp pin ground and polished approximately 1mm and still expect the electric start to work?


No I do not believe you can retard the exhaust cam a tooth on a 07+ WR450. It probably would not run or could hit something. The cam lobes do not look correct when the cam is in that position.
You should be able to use a YZ exhaust cam and somewhere around 1mm supposedly allows proper electric starter use. However I have not done it personally.





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