Replace my 08 yz450f exhaust cam with a WR exhaust cam ,is it ok ?


22 replies to this topic
  • lesi88

Posted September 01, 2009 - 06:37 PM

#1

I have just bought a new 08 yz450f,i love trail 。I don't want take any competition, just for fun,so I need to reduce the power,and of course my yz450f engine would be more reliable.

so i want to:
1.add a GYTR Off-Road Flywheel;
2.Replace my 08 yz450f exhaust cam with a 08 WR450 exhaust cam,not replace the intake cam.

If just replace with a WR450 exhaust cam,need any jetting?
Do I need to replace both intake cam and exhaust cam?
Will the WR450 cam's Auto Decomp system cause my yz450f startup harder?

grayracer513 could give any advice?
thanks very much.

  • lesi88

Posted September 03, 2009 - 04:55 PM

#2

could anybody give some good advice?

  • grayracer513

Posted September 03, 2009 - 06:28 PM

#3

Both those ideas will work, although neither will make the bike any more or less reliable. Why didn't you just buy a WR in the first place?

  • lesi88

Posted September 03, 2009 - 10:06 PM

#4

grayracer513,thanks very much. :ride:

cause YZ is more lighter than WR, YZ can be also mod for trail easily by adding flywheel weight,though the light is an issue.

I think my YZ with above mods would have lower power than a brand new one. After these mods, my mod YZ is as durable as WR? The period between changing oil could be longer?

thanks :)

  • outcast623

Posted September 04, 2009 - 04:06 AM

#5

No mod that I am aware of gives you the benefit of longer oil change periods.. you may be lowering the hp of the bike with a more restrictive cam, but the fact is its still a yz450f get used to the maintenance you bought a "race" bike.:ride:

  • erickdj

Posted September 04, 2009 - 06:42 AM

#6

there's nothing you can do to make the bike go longer between oil changes. The wr cams won't make it any more reliable at all, it will simply kill some of the yz's power. The wr shares pretty much the same engine with the yz except for a few changes, but both are race engines that require frequent maintenance. Don't waste money on wr cams, they will do nothing for you in the long run, you'll just be wasting your money away if you think they will help you to make the bike go longer between oil changes or make it more reliable.

  • moto_xmayhem21

Posted September 04, 2009 - 07:02 AM

#7

Just buy a Q exhaust and some bark busters for it, then hit a trail! There, trailbike!

The only thing that will keep your bike from breaking down is if it just sits in the garage all year. Otherwise, it will need periodic work like all the other bikes.

Besides, the power is different, but to waste all that money on "sucking the fun factor" out of that yz??? Nah, it's gunna do awesome on trails regardless!

Just my opinion:rolleyes:

  • grayracer513

Posted September 04, 2009 - 07:33 AM

#8

I think my YZ with above mods would have lower power than a brand new one. After these mods, my mod YZ is as durable as WR? The period between changing oil could be longer?

You won't be able to go any longer between oil changes, and as I said, none of these mods will make the bike any more or less reliable. It was already on an equal footing with the WR.

If you had bought the WR, it would have the cam, the heavier flywheel, AND a wide ratio trans, giving you a lower first gear more suited to trail riding without sacrificing top speed, plus the option of running lights. You could have reduced the weight of the WR without spending any money on doing so.

  • yamaha227

Posted September 05, 2009 - 02:09 AM

#9

I have just bought a new 08 yz450f,i love trail 。I don't want take any competition, just for fun,so I need to reduce the power,and of course my yz450f engine would be more reliable.

so i want to:
1.add a GYTR Off-Road Flywheel;
2.Replace my 08 yz450f exhaust cam with a 08 WR450 exhaust cam,not replace the intake cam.

If just replace with a WR450 exhaust cam,need any jetting?
Do I need to replace both intake cam and exhaust cam?
Will the WR450 cam's Auto Decomp system cause my yz450f startup harder?

grayracer513 could give any advice?
thanks very much.


What you are doing is a good idea and something i have also thought off, and may do to a 2010 model to set it up for enduro for next year.
You will never get a WR as light as a YZ and if this is your main concern then getting a YZ is the way to go.
I would replace both cams, the inlet and exhaust with WR items. I doubt you will have any starting issues as the YZ cams have auto decomp aswell. Jetting changes will be minimal, just see how it runs first.
Like you said, get the heavier GYTR flywheel, from experience this will help aswell and make your YZ a sweet trail bike with much better forks than the WR (providing they are revalved and setup for you and your riding conditions) and a hell of alot lighter.
Another option to taming it down a bit aswell may be a slightly more restrictive muffler like a Q4. Let us know how you get on :busted:

  • Just_a_trail_rider

Posted September 05, 2009 - 02:21 AM

#10

Besides, the power is different, but to waste all that money on "sucking the fun factor" out of that yz??? Nah, it's gunna do awesome on trails regardless!

Just my opinion:rolleyes:


WR's are fun too! If you were riding enduro's, you'd really appreciate less snap from the motor towards the end of the second or third loops when you are sometimes so damn tired you can't see straight.

I understand the less is more thought process.

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  • Just_a_trail_rider

Posted September 05, 2009 - 02:25 AM

#11

I have just bought a new 08 yz450f,i love trail 。I don't want take any competition, just for fun,so I need to reduce the power,and of course my yz450f engine would be more reliable.

so i want to:
1.add a GYTR Off-Road Flywheel;
2.Replace my 08 yz450f exhaust cam with a 08 WR450 exhaust cam,not replace the intake cam.

If just replace with a WR450 exhaust cam,need any jetting?
Do I need to replace both intake cam and exhaust cam?
Will the WR450 cam's Auto Decomp system cause my yz450f startup harder?

grayracer513 could give any advice?
thanks very much.


You should have gotten the WR to begin with. The aluminum frame models feel much more balanced than the steel frame model that I have. You would not have been sorry.

But since you have the yz, you can definitely tune it down by changing the cams. You can also try putting on the stock wr pipe with the PMB insert. That will dial it back just a bit more. It will still be tons of fun.

  • lesi88

Posted September 06, 2009 - 07:25 AM

#12

Thanks everbody's good advice.

After Adding flywheel weight and WR exhaust cam to my yz,my yz should get a better lower~middle mellow power curve.
This is my main purpose and fortunately both the ideas will work.

There is an another question that is how the engine mods affect the engine durablity.

Everybody knows that YZ shares pretty much the same engine with the WR except for a few changes, the only difference in motor was the exhaust cam, tranny, and fly wheel stuff.
The yz's mainternance is different from WR's though both are race engines that require frequent maintenance.
The power is different,so the maintenance is also different.

In my opinion,WR sacrifice several hp's for increase durability.
With the WR,we can change oil every 1000 km,and the oil quality is not critical as YZ.

Back to my yz,if i add flywheel weight、WR exhaust cam and the stock WR pipe with the PMB insert to my YZ,my YZ'power could be reduced to the level of the WR'S. AS grayracer513 said that "It was already on an equal footing with the WR".
I assume that Since the mod YZ'power is at the same level with the stock WR, the mod YZ's durability should be at the same level with the stock WR.
It seems that after adding mods on my YZ,my YZ'S routine maintenance can be treated as a WR.

Of course,i am just interested in this topic about the YZ'S durability after adding mods.I will still do the maintenance as the yamaha requested.
Somebody thinked that the WR exhaust cam has no effect to the YZ's durability,can we talk about it deeply and give some examples?



Thanks again!

  • grayracer513

Posted September 06, 2009 - 08:19 AM

#13

The yz's mainternance is different from WR's though both are race engines that require frequent maintenance.
The power is different,so the maintenance is also different.


With the WR,we can change oil every 1000 km,and the oil quality is not critical as YZ.

You are treating these statements as fact, when they are not.

The oil quantity in a WR is the same as a YZ, and every bit as critical. The oil in a WR should be changed no less often than that of a YZ when both are used the same way, and the maintenance on both bikes is identical, based on similar uses.

In stock form, a YZ is NOT less reliable or durable than a WR is. Your addition of a WR cam will not make it more reliable than it otherwise would have been when used the same way.

  • motovita

Posted September 06, 2009 - 08:33 AM

#14

I realize that this is a little late but why not get a WR, remove the battery, starter motor and associated wiring. If the WR,s still come with steel sprockets replace it with an aluminum one. I think then the weight difference would be negligible and you would have a better trailbike.
Personally though, I think the electric start is worth it's weight in gold!

  • Sider_steve

Posted September 06, 2009 - 02:03 PM

#15

Does the CDI on an 08 YZ contain the WR ignition mapping as well?
Could simply grounding 1 wire de-tune his YZ enough to make him happy?
Have you taken thje bike for a ride yet?
I can see adding the flywheel weight to smooth out the low end power.
But I see no reason to change cams,that wont effect reliability.
Yamahas recomended oil changes for the YZ's are probably a little tighter because it is designed to be raced. But I would still follow the recomended oil changes for it

  • mywifefarts

Posted September 06, 2009 - 02:17 PM

#16

:busted: :thumbsup: :banana:

You are treating these statements as fact, when they are not.

The oil quantity in a WR is the same as a YZ, and every bit as critical. The oil in a WR should be changed no less often than that of a YZ when both are used the same way, and the maintenance on both bikes is identical, based on similar uses.

In stock form, a YZ is NOT less reliable or durable than a WR is. Your addition of a WR cam will not make it more reliable than it otherwise would have been when used the same way.



  • grayracer513

Posted September 06, 2009 - 04:02 PM

#17

Does the CDI on an 08 YZ contain the WR ignition mapping as well?
Could simply grounding 1 wire de-tune his YZ enough to make him happy?

Nope. The YZ uses a completely different electrical system, and the two CDI's don't interchange. There is no "gray wire" or equivalent terminal on the YZ.

:busted: :thumbsup: :banana:

Once more, in English?

  • lesi88

Posted September 07, 2009 - 07:08 AM

#18

Today i searched the WR forum and got that the WR engine oil grade and period between changing oil are the same with the YZ .That's mean WR is not more reliable than a YZ .
Now i totally realized that WR exhaust cam indeed has no effect to the reliability of YZ.
Maybe the reason is that both WR and YZ are race engines.

Thanks for grayracer513 and other guys who reply my thread!
I will choose a WR exhaust cam for my YZ just for the low-end to middle mellow power curve.

  • Sider_steve

Posted September 07, 2009 - 08:03 AM

#19

Maybe the reason is that both WR and YZ are race engines.

Thanks for grayracer513 and other guys who reply my thread!
I will choose a WR exhaust cam for my YZ just for the low-end to middle mellow power curve.


You said you were going with the GTYR weighted flywheel,correct?
I would suggest trying that modification first,the extra weight on the flywheel should help smooth out the low end power delivery of your 450.
Then if that is not enough then try the WR cam.

  • lesi88

Posted September 07, 2009 - 04:31 PM

#20

You said you were going with the GTYR weighted flywheel,correct?
I would suggest trying that modification first,the extra weight on the flywheel should help smooth out the low end power delivery of your 450.
Then if that is not enough then try the WR cam.


thanks ,that is a good idea!





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