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08 wr450 valve replacement

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Hi guys.

Looking at replacing the valves in my 08 wr450 as preventative maintenance.

Just wondering what the process is. Do I just buy OEM ti valves, new springs and valve guides and put them in or does the head have to be machined for the new valves? My understanding is that you can't use cutting paste on TI valves to seat them, is that correct?

If that's the case where would I get this done? Yamaha dealer?

Cherrs

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13 hours ago, Steven Capp said:

Hi guys.

Looking at replacing the valves in my 08 wr450 as preventative maintenance.

Just wondering what the process is. Do I just buy OEM ti valves, new springs and valve guides and put them in or does the head have to be machined for the new valves? My understanding is that you can't use cutting paste on TI valves to seat them, is that correct?

If that's the case where would I get this done? Yamaha dealer?

Cherrs

Don’t go to the dealer. Take it to a motorcycle machine type shop that does lots of heads. Don’t buy valve guides almost never needed and many put in ones that don’t last. 

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My 07 wr450 I've only had the valves checked twice since I've owned it since 07 new. First wast m as maybe after a yr or 2 second was this last summer after I submerged the hell out of it. Both times they were in spec and runs just fine. 

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On 1/25/2019 at 11:01 PM, Steven Capp said:

Hi guys.

Looking at replacing the valves in my 08 wr450 as preventative maintenance.

Just wondering what the process is. Do I just buy OEM ti valves, new springs and valve guides and put them in or does the head have to be machined for the new valves? My understanding is that you can't use cutting paste on TI valves to seat them, is that correct?

If that's the case where would I get this done? Yamaha dealer?

Cherrs

Have your valves moved resulting in needing to shim them more than twice? If not, I don't think replacement is needed.

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You'd want a machine shop to do a valve job.  Ask around and see who does dirt bike heads (or more specifically, the yamaha 5 valve heads)

Drop the head off with them, and ask them to inspect the head/valves and they will tell you what it needs and how much they charge.

Definitely a good idea to do valve stem seals if they are replacing the valves.  They can grind the seats down, but not Ti valves.

 

But, what makes you think they need replacing?  Have the valve clearances been off?

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There are many different answers you will get to this question.

Yamahas Manuel says when changing valves to use new Ti valves and lap them then not use them ones and instead install new ones, seems odd and expensive

But all I know is I wouldn’t go stainless, if I ever have this issue I’m going oem titanium

Also do a leak down test to even see if it’s needed first

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Titanium valves are coated and if you lap them, you wear through the coating and the valve won't last very long. That's why they say not to use it. 

If you lap using your old valve, well the shape is probably wrong.

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Titanium valves are coated and if you lap them, you wear through the coating and the valve won't last very long. That's why they say not to use it. 
If you lap using your old valve, well the shape is probably wrong.


That’s why I have never understand why the Manuel suggests that lol.

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1 minute ago, Deetle15 said:

 


That’s why I have never understand why the Manuel suggests that lol.

 

What do you not understand?

 

In order to lap you need a sacrificial valve that's the same shape as the one you'll be using. I don't know what options that leaves beyond lap and then use a different new valve. 

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3 minutes ago, toten said:

What do you not understand?

 

In order to lap you need a sacrificial valve that's the same shape as the one you'll be using. I don't know what options that leaves beyond lap and then use a different new valve. 

I guess that was worded wrong. I fully understand you need a sacrificial valve or you would damage the Angles used to seat them it just seems wild to me that the specifications between the valve used for lappingAnd the new one will be using can you sue for sa and the new one will be using  R machined well enough to  hold the pressures 

 I have  Cut and  lapped many valves also replacing the valve seats  doing them for  Briggs  and Stratton world formula and animal WKA engines making them run on alcohol and basically  pushing the engine to the absolute maximum performance and everything has to be in spec if the engine  wins the race it goes through tech getting tore apart and having everything checked to make sure there was no cheating  but we always need to  install new valve seats  and then stake  them in  place  sorry for incorrect spelling Or anything wrong I am currently driving and using dictation

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I think that modern manufacturing standards are good enough that you can do it. 

 

It used to be that there were wide enough tolerances in bore sizes that you'd get A, B, C pistons that weren't for overbore, they were for differences. Not anymore. 

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1 minute ago, toten said:

I think that modern manufacturing standards are good enough that you can do it. 

 

It used to be that there were wide enough tolerances in bore sizes that you'd get A, B, C pistons that weren't for overbore, they were for differences. Not anymore. 

I know machining specs are good, but how about for a 5 valve does it require 10 or 8? Because of exhaust being the same and 2 intakes the same with a odd middle intake? 

Just curious if the lapping stresses enough to make it require them all really 

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3 hours ago, toten said:

....It used to be that there were wide enough tolerances in bore sizes that you'd get A, B, C pistons that weren't for overbore, they were for differences. Not anymore. 

Theres still A, B, C pistons out there for bikes of today, even for our bikes. Not all are listed as it, but by looking at the specs you can easely find pistons with 1 or 2 thoudsands of a milimeter over stock size. :) 

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