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GSXR750 cracks in head between valve pockets as well as spark plug holes

Discussion in 'Tech' started by CB186, Apr 9, 2022.

  1. CB186

    CB186 go f@ck yourself

    Pulled a race motor apart for a friend and found that 3 of the 4 cylinders have cracks running between valve pockets, and/or the spark plug holes. Stock head other than decked .010". 2 seasons on the build.

    Anyone ever see this happen before? I'll be putting a different head on for the rebuild, just surprised to first d this.
     

    Attached Files:

  2. TurboBlew

    TurboBlew Registers Abusers

    that looks like it can be fixed if the head isnt warped
     
  3. RM Racing

    RM Racing Tool user

    Fixing more costly than replacing, plus heat will just warp valve seats and surface requiring valve job and surfacing, possibly also seat replacement. You can send to Star Racing in Americus, GA for evaluation.. That head is basically trash.
     
  4. CB186

    CB186 go f@ck yourself

    Yeah, that was my thought. It would be different if it was ported, but more work than its worth for a stock head.
     
  5. Steeltoe

    Steeltoe What's my move?

    Water froze in the engine over the winter?

    Dropped on the shop floor?
     
  6. beechkingd

    beechkingd Well-Known Member

    Maybe it was run too lean?
     
  7. ibidu1

    ibidu1 Well-Known Member

    Ive had oil seals blow out on a gsxr 750 motor, and have blew up a few. But never seen tiny cracks in the head. Did the bike have an aggressive tune on it? Were the plugs oem? Maybe from detonation they formed, or just overheated and cooled repeatedly.

    As cheap as parts are for the 750, its good you are replacing it. Its not worth fixing imo! It can be done, but with a lot of machining needs to be done and measuring compression.
     
  8. CB186

    CB186 go f@ck yourself

    I have a feeling its tune related. I told him it needs to go back on the dyno after the injectors get cleaned.
     
    418 likes this.

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