Yz450 worn exhaust cam journal, Cowboy repair methods.


16 replies to this topic
  • Bigdong

Posted June 15, 2010 - 09:59 AM

#1

I have a yz450 that at some point i think the exhaust cam must have seized as there is discolouration and some metal transfered from the housing to the cam itself.

My question is, if i rub down the housing for the cam to remove the roughness and excess metal aswell as clean the cam slightly, will the bike run for long? Or is it just going to end up going to peices.

I have already smoothed off the housing and the cam and it turns when in the housing very smoothly and does not move about.

thx in advance for your replies.

Edited by Bigdong, June 15, 2010 - 10:38 AM.


  • crf450319

Posted June 15, 2010 - 10:52 AM

#2

I would guess that an increase in tolerance after removing the metal in question between the cam and the housing may work for a while, but would more than likely end up causing a lot more issues down the line.

Consider the cost of a new exhaust cam ($140 US) and the cost of a new cam holder in comparison to the cost of a complete head. Do you want to risk wrecking the whole head for a quick fix ?

I personally, would replace the cam & holder.

  • Bigdong

Posted June 15, 2010 - 12:18 PM

#3

hi and thanks for the reply,

Unfortunatly the cam took metal of the head where it is held in place so that is where i have "sanded" down a bit to smoothen it off. The cam is also smoothed off and looks decent although you can see wear. As for the holder itself , i have been led to beleive that the holders are matched to the heads and therefore to get one that fits correctly would mean buying a whole head anyways.

An option would to buy a holder off ebay second hand but again it would not be matched to the head. :thumbsup:

  • grayracer513

Posted June 15, 2010 - 12:49 PM

#4

I personally, would replace the cam & holder.

If you had a CRF, you could do that. The cam in the YZF rotates directly in the head, and the caps are not sold separately. Engine Dynamics, Millennium Technologies, and others can repair the head economically, though.

  • Bigdong

Posted June 15, 2010 - 01:10 PM

#5

If you had a CRF, you could do that. The cam in the YZF rotates directly in the head, and the caps are not sold separately. Engine Dynamics, Millennium Technologies, and others can repair the head economically, though.


Going off topic on my thread but your saying a crf has seperate cam holders. Is this true with an suzuki rmz aswell or strictly the hondas?

I ask because this is the second time i have seen it happen to a yam and it makes for a major operation.

  • crf450319

Posted June 15, 2010 - 03:49 PM

#6

If you had a CRF, you could do that.


Subconsciously staying true to my user name I suppose.

I would still look at replacing the cam and having the head professionally repaired, there's got to be a performance engine shop in the UK that can fix it for you (for a reasonable cost) ? What year is the bike ?

  • grayracer513

Posted June 15, 2010 - 03:53 PM

#7

Going off topic on my thread but your saying a crf has seperate cam holders. Is this true with an suzuki rmz aswell or strictly the hondas?

Hondas only. You don't have to keep doing this to your Yamahas, you know.

  • sacfelix

Posted June 15, 2010 - 10:15 PM

#8

I sent a head from a 06YZ450 with cam journal damage to Engine Dynamics in Petaluma, CA and they fixed it for $130. I had it back in a couple days.

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  • Bigdong

Posted June 15, 2010 - 10:48 PM

#9

Its only an 03, Unfortunatley sending to ca might be a problem :thumbsup:.

Ok well i have another head that i could use but i noticed that where the actual valve rods go through the hole is too big. Its like there is meant to be some sort of sleeve in it. Is it a valve stem seals that i need? i have the online manual but it doesnt say much about this area. I can put up photos if needed.

Ive been looking at getting a suzuki but dreading this happening to it aswell. Why is it honda is the only one with replacable journals. =p

  • KJ790

Posted June 16, 2010 - 05:14 AM

#10

Its only an 03, Unfortunatley sending to ca might be a problem :thumbsup:.

Ok well i have another head that i could use but i noticed that where the actual valve rods go through the hole is too big. Its like there is meant to be some sort of sleeve in it. Is it a valve stem seals that i need? i have the online manual but it doesnt say much about this area. I can put up photos if needed.

Ive been looking at getting a suzuki but dreading this happening to it aswell. Why is it honda is the only one with replacable journals. =p


Sounds like you need valve guides and seals in your other head.

Honda has a removable cam holder because with the way they designed the single overhead cam, you can't really get to the valve springs with the cam holder in the way.

  • Bigdong

Posted June 16, 2010 - 07:56 AM

#11

Sounds like you need valve guides and seals in your other head.

Honda has a removable cam holder because with the way they designed the single overhead cam, you can't really get to the valve springs with the cam holder in the way.


Yeah valve guides and seals. Are these easy enough to install?

Edit:- just looked it up. Has anyone tackled this themselfs? I wonder if i could just stick the head in the oven and pop them in myself or would yous reccomend getting this done professionally?

  • grayracer513

Posted June 16, 2010 - 08:07 AM

#12

Valve guides have to be installed by a competent small engine machinist. The reason is that regardless how well or how precisely the guide is inserted, it will NEVER center up on the original valve seat center. Even if the seat wre not worn, and it will be, they would then need to be recut/reground, or the valve will not seal.

Anyone doing this job needs to have had experience in working with coated titanium valves, since the finish of the seats is critical to the longevity of the finished head, and Ti valves can never be lapped.

  • Bigdong

Posted June 16, 2010 - 08:14 AM

#13

Valve guides have to be installed by a competent small engine machinist. The reason is that regardless how well or how precisely the guide is inserted, it will NEVER center up on the original valve seat center. Even if the seat wre not worn, and it will be, they would then need to be recut/reground, or the valve will not seal.

Anyone doing this job needs to have had experience in working with coated titanium valves, since the finish of the seats is critical to the longevity of the finished head, and Ti valves can never be lapped.


Ok thanks, that clears that up. Any idea what this would cost to have done?

Also are all yam valves titanium? and if not how can i tell. The other head has Minor damage but would be fine if i can lap the valves into it.

Edited by Bigdong, June 16, 2010 - 08:32 AM.


  • grayracer513

Posted June 16, 2010 - 08:33 AM

#14

You'd need to check your local prices. Also, it's unusual for there to be any major wear in the guides on theses engines because of their design. If the valves are that loose, either the valves or the head itself may be the wrong one for the engine.

  • Bigdong

Posted June 16, 2010 - 08:37 AM

#15

You'd need to check your local prices. Also, it's unusual for there to be any major wear in the guides on theses engines because of their design. If the valves are that loose, either the valves or the head itself may be the wrong one for the engine.


No, whats happened is i have a spare head that bounced a valve in the past but is in good enough condition to reuse, but all the valve guides have been taken out by whoever removed the valves from it.

But as for pricing to get new guides, are we talking big bucks?

  • grayracer513

Posted June 16, 2010 - 09:44 AM

#16

Not really. The guides themselves don't cost much, and with the right tools, there's not a lot to installing them. Then you add the labor for a typical valve job; ~$125-175 USD.

The valves are what will kill you $!

  • sacfelix

Posted June 16, 2010 - 01:10 PM

#17

I found a complete OEM valve kit for $327 from Honda East Toledo on ebay with $10 shipping.
http://cgi.ebay.com/...sQ5fAccessories





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