How do these valves and seats look? Not Good!


14 replies to this topic
  • honyam83

Posted February 08, 2009 - 04:41 PM

#1

Hello again, I'm rebuilding the top end on my 2001 YZ 426 f, just traded for it in Decemberhttp://www.thumpertalk.com/forum/images/smilies/banghead.gif. This is the first time that I have ever been this deep into any kind of head, so I'm not sure what I'm looking at. I was told that the top end was done last spring, I guess that didn't include valves I was hoping that some of the more experienced wrenches could give me some feed back on these pics. sorry about the quality. My wife currently has the good camera. Even thought I don't know what I looking at I'm sure these aren't good. I was thinking about replacing them with ss, and was wondering if lapping the valves would be sufficient. Or if I need the seats to be finish ground, maybe cut? Thanks honyam



http://s599.photobuc...t=1234145348273

  • alwho44

Posted February 08, 2009 - 04:49 PM

#2

love to check out your pic` but facebook requires login sorry

  • grayracer513

Posted February 08, 2009 - 06:07 PM

#3

Can't tell. You posted links to the thumbnail sized pix.

  • honyam83

Posted February 08, 2009 - 06:11 PM

#4

Okay, let me try again. Can you tell it is my first photo post?

  • BBrown626

Posted February 08, 2009 - 06:22 PM

#5

Hello again, I'm rebuilding the top end on my 2001 YZ 426 f, just traded for it in Decemberhttp://www.thumpertalk.com/forum/images/smilies/banghead.gif. This is the first time that I have ever been this deep into any kind of head, so I'm not sure what I'm looking at. I was told that the top end was done last spring, I guess that didn't include valves I was hoping that some of the more experienced wrenches could give me some feed back on these pics. sorry about the quality. My wife currently has the good camera. Even thought I don't know what I looking at I'm sure these aren't good. I was thinking about replacing them with ss, and was wondering if lapping the valves would be sufficient. Or if I need the seats to be finish ground, maybe cut? Thanks honyam

http://i599.photobuc..._valveseats.jpg

http://i599.photobuc...ntakevalves.jpg

http://i599.photobuc...haustvalves.jpg


While the pix are tiny and I can't see the condition of the parts, there are a few e-bay stores that offer good deals for kits with the valves, springs, seals and keepers. I believe you'll need a shop to cut your seats on a machine. You are not supposed to lap the valves due to a coating they have on them. Many say SS is not as good as the TI valves. I believe that is largely due to the added weight and the stress it will place on the springs. With the kit pricing it is hard to beat the OEM parts. I am in the middle of a head and valve replacement and waiting on parts. It is my first time for this repair as well. So far it looks pretty easy.
Good luck.

  • honyam83

Posted February 08, 2009 - 06:30 PM

#6

Can you try my link again please.

  • honyam83

Posted February 08, 2009 - 06:45 PM

#7

Even if I go with SS valves I should not lap them?

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  • 426 NOOB

Posted February 08, 2009 - 07:25 PM

#8

Even if I go with SS valves I should not lap them?


I wouldnt, motor builders say never to lap any modern 4 stroke valve due to special coatings. Just nave the seats cut professionally.

Read:
http://www.thumperta...ight=lap valves

  • matt4x4

Posted February 09, 2009 - 06:45 AM

#9

Ok, if you follow the original links to the thumbnails and then remove the "th_" from the links you get the full images:

Posted Image
Posted Image
Posted Image


And just looking at these - they are done - you're actually VERY lucky this didn't blow up on you.
Definitely have the seats cut professionally - and go with hte SS valves, springs and hardware.

  • grayracer513

Posted February 09, 2009 - 08:11 AM

#10

And just looking at these - they are done - you're actually VERY lucky this didn't blow up on you.

And how did you arrive at that conclusion?

I see no abnormal or excessive wear on anything, although the poor focus makes things a little hard to see. Wear, yes, and no way of knowing how much longer they would run before sinking, but nothing out of the ordinary. What were the valve clearances before the engine was dismantled? Probably should still go ahead and do a valve job with the stainless valves and springs from a 2000 model.

What is odd is the lack of carbon and the color of the exhaust valves. That suggests that the engine was very hot, and/or had coolant in the combustion chamber. Have the head checked for flatness and cracks.

  • matt4x4

Posted February 09, 2009 - 09:44 AM

#11

I based it on the coating being worn off on the intake valves, since it's worn off, that leads me to think there isn't much life left in them. The hot spots on the exhaust stems didn't make me feel any more confident about the valves either.

I agree too that the white exhaust valves - they shouldn't look like that.

What do you make of the hot spots on the stems Gray (I didn't like the looks of that at all)? Almost like the valves got excessively hot...

  • grayracer513

Posted February 09, 2009 - 10:29 AM

#12

The white carbon would tell you they were hot, as I mentioned. As for the coating, you cannot tell that it's worn off simply by the fact that there's a bright contact band around each valve. That will happen as the seat wears to a full match with the valve face.

Even if you had them in your hands it might be quite difficult to determine that, since the coating is so very thin (often <.0004") that there's no practical way to measure the depth of a wear pattern that would be within the depth of it. Of course, ANY perceptible wear would be through the coating.

These two exhaust valves show that. The one at the left is normal/healthy, the one at right shows obvious wear, and is thus worn out. (Note the apparent ridge at the edges of the contact band)

Posted Image

But they not necessarily be in danger of dropping a head on the piston until they got to be somewhat worse, more like these intakes from a 250F:

Posted Image

The best indicator that you really have of when they reach a state when they're worn through is valve clearance. When they need to be shimmed looser, and then soon after that, they need it again, they are definitely done. Beyond that, all you can do is take your best guess.

  • honyam83

Posted February 09, 2009 - 03:52 PM

#13

Here are the clearences (exhaust <.03 and .2) intake (.09 .06 .15).
It was leaking coolant from the lower cylinder gasket. I will have the head cchecked out. Thank you

  • grayracer513

Posted February 09, 2009 - 05:16 PM

#14

Probably be a good idea to replace the valves, by the looks of that. Use the stainless ones. The seats look salvageable.

  • 642MX

Posted February 09, 2009 - 05:24 PM

#15

My valves look a little white too, but not quite that much white. I blame it on the lead in my gas, since the inside of the exhaust looks like that too.





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