OEM valve problems?

3 replies to this topic
  • got5steelman

Posted November 20, 2009 - 06:56 AM


Does anyone know of any issues with Yamaha OEM valves breaking? I called MXtime and they said that OEM yamaha valves are having alot of problems breaking off at the neck of the valve. I think he is just trying to sell me his valves. I have over 100 hours on my OEM parts on a 05 YZ450 now, I am getting ready have the valves, springs, seats replaced and need a reliable shop to have the service done, I already have all the OEM parts and need a good shop that will install all the parts and set up the head correctly. Anyone have suggestions.

  • grayracer513

Posted November 20, 2009 - 07:17 AM


I think he is just trying to sell me his valves.

He clearly is. OEM valves break at the head for two reasons:

  • They hit the piston because of timing chain failure. It might be nice if they would resist breaking under this condition a little better, but it wouldn't often make a difference in the amount of damage done.
  • They break due to stem flex when owners try to run them with extremely worn faces for too long. Once the valve has been reshimmed more than .10 mm from its build shim size, it should be taken out of service.

OEM valves do not generally just drop a valve head in the absence of any other problem (the '06 250F DID have trouble with this, but that was a different situation), so you're getting a smoke enema.

You found a shop to redo the seats etc., then?

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  • got5steelman

Posted November 20, 2009 - 09:31 AM



I am still looking for a good reliable shop to install the oem parts in the head, Does anyone know of any? Alot of shops want you to buy their valves etc. I need a place that will install my OEM parts and cut the seats correclty to match the new valves.

  • grayracer513

Posted November 20, 2009 - 09:57 AM


I don't know of any on the East Coast, but there is EDCo in California, Millenium Technologies in Wisconsin, and TT moderator Eddie Sisneros at OTD Cyclesports, in Denver.

Eddie's probably the best choice, but they're all good.

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