Broken Valve Bucket


14 replies to this topic
  • sparkyz

Posted January 24, 2010 - 11:33 AM

#1

Hi, I was just in the process of replacing the head gasket on my 03 YZ450 and I also ended up finding that the valve lifter bucket on one of the exhaust valves is broken. According to the service manual it says if there is any damage to the bucket to replace the bucket and the head. I was wondering if anyone has had a machine shop clean up the area successfully? I'm also trying to figure out what caused the bucket to break. I cannot find anything wrong with the valve or spring so it looks like the damage is only concentrated to the bucket and the bore the bucket rides in. Any help is greatly appreciated, thanks.

  • grayracer513

Posted January 24, 2010 - 01:12 PM

#2

How far down the bore is the head damaged?

  • sparkyz

Posted January 24, 2010 - 02:14 PM

#3

Here is a picture that hopefully shows it better than I can describe it. It was difficult to get a good picture but hopefully this one shows it well enough. I also just noticed the top of the valve is smashed down and mushroomed out a bit and when I removed the head I saw there was coolant in the valve relief pocket on the piston that goes with this valve so my guess as to what caused the damage at this point is that the pocket had enough fluid in it to damage the valve.

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Edited by sparkyz, January 24, 2010 - 08:44 PM.


  • sparkyz

Posted January 24, 2010 - 08:46 PM

#4

For reference I would say the scoring goes down approximately a half inch measuring down from the cam journal.

  • grayracer513

Posted January 24, 2010 - 08:57 PM

#5

Parts of that are pretty ugly. But I'd give EDCo a chance to look at it before I tossed the head. Might be able to fix it for $2-300, or even less, rather than $800+.

Or, maybe a used one.

  • sparkyz

Posted January 25, 2010 - 12:50 PM

#6

Thanks for the help grayracer513. I got a chance to go by a local shop today and they said it isn't too bad and should clean up without a problem. They machine it and then use a slightly larger bucket from a Kawi or Honda. They said about $80 for the work and the bucket so all I need is a new valve... So it isn't as bad as I had feared. Thanks again for the help.

  • outbound6

Posted March 07, 2011 - 01:44 PM

#7

I just had the same thing happen. How much other damage was done by this busting up? Did it clean up ok?

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  • sparkyz

Posted March 12, 2011 - 09:17 PM

#8

The valve guide for the damaged valve was also damaged. The shop said it wasn't a big deal to replace it, but he had a good core head sitting in his shop and just let me have that one for the same price to save some time.

  • brentn

Posted March 13, 2011 - 12:06 AM

#9

Interesting, goes to show that a head gasket failure can cause head damage and not just burn coolant and oil. So I guess the seat was ruined as well?

  • grayracer513

Posted March 13, 2011 - 07:10 AM

#10

The condition of the head gasket has nothing whatever to do with the broken tappet. To assume that it did makes no more sense than saying that the head gasket caused the rear hub to break.

  • brentn

Posted March 13, 2011 - 08:21 AM

#11

The condition of the head gasket has nothing whatever to do with the broken tappet. To assume that it did makes no more sense than saying that the head gasket caused the rear hub to break.


gotcha.

I suppose if it was hydro locked there would be piston/rod issues not valve ones?

Edited by brentn, March 13, 2011 - 08:39 AM.


  • grayracer513

Posted March 13, 2011 - 02:39 PM

#12

True. Thing is there's no causal connection from any condition that would result from a head gasket problem and the broken tappet. The most probable would be heat the lead to a seizure of the cam or the tappet itself, but if there were a heat issue, the piston would be far more apt to seize first.

I think it's just coincidental that this was discovered when the gasket was being replaced.

  • brentn

Posted March 13, 2011 - 03:54 PM

#13

thx for the info, learning here :thumbsup:

  • sparkyz

Posted March 16, 2011 - 09:52 PM

#14

The thing that made me think that the head gasket had something to do with it was the fact that the top of the valve stem was mushroomed. That tells me that it had a strong force pushing on it from both directions causing it to mushroom. I was thinking that at the same time this also caused the bucket to be pushed into the side of its bore.

When the head was removed the only spot on the piston that had any coolant in it was in the valve relief pocket coinciding with the damaged valve. There were also no signs of damage to the piston from the valve striking it or any other forms of damage.

The shop that did the work also inspected my cams and their journals and agreed that they looked fine.

If only the bucket were damaged I would agree that the head gasket had no influence, but because of the top of the valve I would think the fluid on the piston caused the damage.

  • grayracer513

Posted March 17, 2011 - 08:28 AM

#15

If only the bucket were damaged I would agree that the head gasket had no influence, but because of the top of the valve I would think the fluid on the piston caused the damage.

Nope. The top of the valve wash mushroomed by the same event that broke the tappet. What did that was probably the temporary formation of an excess of valve clearance because of the tappet or valve stem sticking, a broken valve spring, or a chunk of carbon lodging between the valve and seat. There is no possibility that coolant on top of the piston could cause the valve to be pushed up into the tappet without first hydro-locking the piston.





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