Would you replace or run them?


7 replies to this topic
  • 02WR426Cali

Posted February 01, 2009 - 01:28 PM

#1

Here are some pics of my valves from my 02 426. I am giving the top end a refreshening and wanted to inspect the valves while I replace the piston (which had no wear). I measured the valve seat width, stem O.D. and both measured like new. The manual gives runout as well as "new" specs and all 5 were very close to "new" specs and nowhere near runout. The seat width does look a little bigger in the pics due to lighting however. The tips are multicolored telling me that some of the coating has worn but not all. I have never had to adjust any of these and have never had any hard starting problems. The clearance all measured within spec although it was closer to minimum spec rather than in the middle. Tell me what you would do.

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  • 642MX

Posted February 01, 2009 - 03:37 PM

#2

If it was my bike, I'd replace them.... after all, they are 7 years old. If you replace them, be sure to have the seats refinished and replace the valve springs and seals too.

  • 02WR426Cali

Posted February 01, 2009 - 04:26 PM

#3

If I do end up replacing them I will use parts from a 00 426, oe parts. I know I have to get more than the valves, I need springs, cotters, retainers, etc.

  • matt4x4

Posted February 02, 2009 - 06:30 AM

#4

it looks like the coating is worn off on the 3 intake valves at the stem and seat surface, so I'm not sure how they can still measure in spec, I'd be replacing them without a second thought. It's cheap insurance - well, not super cheap, but cheaper than having one drop any time soon.

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  • 02WR426Cali

Posted February 02, 2009 - 07:22 AM

#5

Yeah the coating does look a little worn, especially on the seats. But everything is well withing spec, the seats face widths all measured well under the 1.6mm runout. They all measured around 1.2mm or under, with new being 1.1-1.3mm I believe.

I'm not sure what Grayracer has against me but he refuses to give me advice. What's up with that?

  • grayracer513

Posted February 02, 2009 - 07:24 AM

#6

The exhausts look excellent, and the intakes look OK, but that's extremely difficult to tell, since the Nitride coating is very thin. Then again, the fact that the valve clearance is still good (it was very likely built at the low edge of the specified range) indicates that there is no appreciable wear at the face.

So, here's the problem you have: You have no idea, and no way to definitively determine when the coating will wear through and the valve(s) start sinking, or when, if ever, a valve may drop a head from fatigue. At this point, to replace them would certainly be to give up some of their serviceable life, but how much? A year? Two years? Two weeks? Will the valves just suddenly tighten when they go bad, or will one break and do $2000 worth of damage? (Let me know if you figure out how to get a good solid answer to those questions. They are universally problematic when rebuilding anything.)

If I had a 426, and I had any reason to replace the valves, I'd use the stainless valves from an '00 model, along with the '00 springs and retainers. They are far less expensive, very reliable, and easily good enough for the vast majority of 426 owners.

  • hillclimbguy

Posted February 02, 2009 - 10:36 PM

#7

That sounds like good advice to me.

  • Wes Woodin

Posted February 03, 2009 - 05:22 AM

#8

Here are some pics of my valves from my 02 426. I am giving the top end a refreshening and wanted to inspect the valves while I replace the piston (which had no wear). I measured the valve seat width, stem O.D. and both measured like new. The manual gives runout as well as "new" specs and all 5 were very close to "new" specs and nowhere near runout. The seat width does look a little bigger in the pics due to lighting however. The tips are multicolored telling me that some of the coating has worn but not all. I have never had to adjust any of these and have never had any hard starting problems. The clearance all measured within spec although it was closer to minimum spec rather than in the middle. Tell me what you would do.

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Change them:thumbsup:





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