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  1. #1

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    Question Cause of death on 720 GTI?

    Hi everyone Iím looking for help as to the cause of death on my 720 GTI Single Carb. Oil system was working, carb clean, rotary valve was tight and exhaust bolts gaskets seemed tight. This motor had about 60hrs on it. Compression was 150psi / 65psi.



  2. #2

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    Is the video bad, not enough info?

    I'm trying to get in touch with Full Bore Racing to see if this is something they will cover under warranty. I just wanted to know what you guys think.

  3. #3
    My Jet Ski drinks more than yours Glenozzy's Avatar
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    can't tell or see any damage, try a new head gasket and run compression test again or take the motor apart something has to cause the loss in pressure

  4. #4
    Myself's Avatar
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    It's a tough call without actually tearing it down but I see what appears to be greyish goo in that sides exhaust port. Possibly a leaking exhaust manifold gasket was allowing water intrusion during the back pressure pulse wave.

  5. #5

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    This is what I’m concerned about. Though as time passes I’m concerned Full Bore is probably MIA until fall so maybe I should just fix it.
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  6. #6

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    My boroscope just came in the piston wash is the same for both cylinders. Only one shows damage.

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  7. #7
    Myself's Avatar
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    That grey goo is a watery exhaust oil mix. You had water intrusion from a gasket somewhere, probably the exhaust manifold. Those surfaces need to be dead flat.

  8. #8

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    Should I pressure test the cooling system to make sure it wasn’t the head gasket?

    So, being an engine builder, I assume you wouldn’t cover this under a warranty if it was you. I just found out they used 84mm pistons, so I guess I’d have to re-sleeve.

    Also would you say the piston wash looked good?

  9. #9
    This is how I run a jetski shop in the desert nmpeter's Avatar
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    Quote Originally Posted by kingofl337 View Post
    Should I pressure test the cooling system to make sure it wasn’t the head gasket?

    So, being an engine builder, I assume you wouldn’t cover this under a warranty if it was you. I just found out they used 84mm pistons, so I guess I’d have to re-sleeve.

    Also would you say the piston wash looked good?
    only an SBT engine under warranty would be covered for something like this

    you'd have to have some really good will with anybody else to eat the cost of that failure, depending on what their invoices say

    when I installed SBT engines I had a pro rated labor schedule for the replacement if the engine blew from something I was responsible for.

    100% for the first 30 days 50 hours and then less and less as time rolled on

  10. #10
    Myself's Avatar
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    Quote Originally Posted by kingofl337 View Post
    Should I pressure test the cooling system to make sure it wasn’t the head gasket?

    So, being an engine builder, I assume you wouldn’t cover this under a warranty if it was you.
    If it were a head o'ring the piston tops would be clean. The wash pattern looks great. Cover it under warranty.....hmmm......I guess that depends, did you get sent cylinders with a pitted and wrecked exhaust gasket surface? Every good machinist trues EVERY mating surface.

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