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  1. #1

    VX cam caps have stress cracks

    I have a 2008 VX Deluxe, 178 hours, I pulled the valve cover off because it was all stress cracked and ugly, I saw the exhaust cam caps are also stress cracked. Everything else looks good but I want to know if I can just buy some used caps from ebay and bolt them on or do I need a whole new head or what?


  2. #2
    Work Harder, Millions on Wellfare Depend On Us! ultramaxracing05's Avatar
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    Post a picture but I know these are just casting marks and completely normal, its just on the surface and not in the inside. I would not change the caps as the ones you buy could have a bigger tolerance and you will create a problem, where one doesnt exists.

  3. #3
    Quote Originally Posted by ultramaxracing05 View Post
    Post a picture
    I didnt get any pics when I had the valve cover off but I found and ebay listing that looks exactly like mine. https://www.ebay.com/itm/2005-Yamaha...wAAOSwEzxYONY3

    Theres no way that is normal casting marks. Those are stress cracks, the valve cover I replaced has cracks completely through from one side to the other. That is structural at that point and not cosmetic.

    What are the bearing clearance measurements? Can caps just be swapped? As long as the bearings are within spec and caps can be swapped it should be fine.

  4. #4
    Work Harder, Millions on Wellfare Depend On Us! ultramaxracing05's Avatar
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    This one seems to have the cracks as well, I dont know the specs on the tolerance for the MR1 engine. I never heard of a valve cover having structural cracks, unless it was slammed with an object. I know all the engines have them artificial looking stress cracks thats just normal.

    Buy what ever pleases you, without pictures we cannot help you.

  5. #5
    The ebay cap I posted looks identical to mine(Im not pulling the valve cover back off for a pic). The intake cam side doesnt have any cracks, I have seen lots of pics of cam caps that dont have cracks and only a few that do so its not some casting lines. The one on the ebay listing you can see a few go all the way through, thats structural failure).
    Heres the valve cover https://i.imgur.com/gwzP47Q.jpg https://i.imgur.com/JOSFEyM.jpg https://i.imgur.com/8ntMnfe.jpg These cracks go all the way through. Thats not normal. No aluminum casting manufacturer would allow that to pass QC.

    I am just trying to find out if cam caps are fitted and then machined/sized to the head/cam or if they are a separate part that are interchangeable if they are within spec(and what that spec is). Surely this knowledge that exists.

    Quote Originally Posted by ultramaxracing05 View Post
    This one seems to have the cracks as well, I dont know the specs on the tolerance for the MR1 engine. I never heard of a valve cover having structural cracks, unless it was slammed with an object. I know all the engines have them artificial looking stress cracks thats just normal.

    Buy what ever pleases you, without pictures we cannot help you.
    Edit:
    Nevermind, I just called SBT, cracks are definitely not normal, theres no manufacturer specs for the cam bearings(for some reason)but they just need to be round and not scored and they should work.
    Last edited by mars22; 10-22-2020 at 03:09 PM.

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