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  1. #11
    So I pulled the head off and the Oil pressure regulator and found the following issues.

    The head as expected has a nice crack near the cam chain oil tensioner feed point, Thats a solid area for a crack to form!! Shit Metal!



    Here is a photo of what we were expecting with the oil pressure regulator, As you can see the from the impact marks on the cover plate its trying really hard to reduce the pressure and is not getting a chance too, interesting enough as you can see in the next photo when the valve is fully open the holes on the regulator are not 100% exposed.




  2. #12
    Lake Lion
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    Wow, if this is the fix ........

  3. #13

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    I am a disinterested Sea-Doo/former Waverunner owner but I would like to inject some wisdom which I have acquired after working through major problems with skis from both brands. Do your best to not get mad at Yamaha-they will only deny everything and won't help you get your ski running any sooner. Owners in this community know there are problems and many of them have been fixed by very talented individuals or aftermarket companies. I would focus on finding these resources as your goal should be to get your ski running for the next race rather than getting a fair resolution from the manufacturer.

    This is just my two cents.

  4. #14
    The last photos I posted didnt show the damage that well and I was in a bit of a rush when I posted them.
    I had the chance to get some decent photos over the weekend that shows what happens when you put a flash on a GP1800. (apparently)







    The head is going to an engine shop to get measured up for metal thicknesses in the areas where it failed and then compared to others.
    From initial measurements there is an estimated 3.5mm of metal where the cracks are
    Surprisingly if it didnt crack all the way through to the outside you would never know that the inside had failed.

    I have a SHO head on the way to be fitted, it will be interesting to compare the two heads in the areas where the cracks are.

    I mean if they had of just beefed up these areas by not shaving off so much metal, I would have just had an exhaust cam missing a Welch plug and I wouldn't have ever known until it seized haha

  5. #15
    MSX 150 guy lives on Mr. GP1800's Avatar
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    I’m not buying that the cracks are caused by running a tune. There are so many people running around with tunes not cracking heads. It’s probably an issue with the casting of the head itself. My guess would be that if it’s going to crack it’s going to crack whether you are stock or running a tune. There are plenty of people revving the crap out of these motors and not cracking heads

  6. #16
    Click avatar for tech links/info K447's Avatar
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    Quote Originally Posted by Luke1.8 View Post
    ... photos ... that shows what happens when you put a flash on a GP1800. (apparently)



    ...
    Where exactly on the engine exterior is this crack location?

  7. #17
    Its a hairline around this area, It cant be seen just by looking at it but the oil flows freely when running at Idle.


    I will pressure test this under 10 hour head and hopefully make a video showing all the bubble

  8. #18
    Thought I would close my chapter on this thread (for now)

    I have finally got the GP 1800 repaired and winning motos. Its now fitted with head number 4 and going great.

    I went down the path of using second hand heads, one didnt work one is going great.

    Its currently fitted with a 2012 HO head with with 146-149 psi across all 4 pots.
    Im running the 8650 tune and getting around 122km/h going off the gopro gps speedo

    What was the cause of the heads cracking? Shit heads..
    Head number 3 cracked on installation head number 4 was installed the exact same way and as you can see from the video, taking every bit of abuse I can throw at it.

    Verdict- Yamaha, make stronger heads!

  9. #19
    outnumbered's Avatar
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    Quote Originally Posted by Luke1.8 View Post
    Its a hairline around this area, It cant be seen just by looking at it but the oil flows freely when running at Idle.


    I will pressure test this under 10 hour head and hopefully make a video showing all the bubble
    Is this picture of the oil feed line under the exhaust manifold? Great thread by the way.

  10. #20
    Hey Mate,

    Thats the oil feed for the chain tensioner on the inlet manifold at the front of the engine.
    The crack runs horizontal all the way around that point and if you look at the other photos you can see where the crack continues on the inside where the timing chain runs.

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