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  1. #1
    banshee350racer's Avatar
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    Strange knock from motor

    I just did my first start up of the brand new motor I built myself. Everything turned over with no problem before I dropped it in. It started on first try with no problems and revs up with no problem. The only thing is when I let go of the throttle and the motor revs down there is a knock on the way down, but the knock is too slow to be something hitting. I think my 01 Sea Doo XP does the same thing but I canít remember exactly. It has a -.03 milled head but I used 93 Oct fuel premixed with oil. Anyone have any ideas?


  2. #2
    same for me it's appears to be normal with this motor

  3. #3
    banshee350racer's Avatar
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    Good, now I feel much better anyone else have this same occurrence?


  4. #4
    All hail the Chief! fullboogie's Avatar
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    Is it a KNOCK or is it a kack kack kack. Sounds silly when I type that. Anyway when I went higher compression and free flow it began cackling on decel. Ever been to the drag strip and heard an alcohol engine cackle? Similar sound. I think you're fine.

  5. #5
    Altezza01's Avatar
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    sounds like piston slap.

  6. #6
    All hail the Chief! fullboogie's Avatar
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    Piston "slap" is not normal. That would indicate excessive clearances.

  7. #7
    Altezza01's Avatar
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    sorry fullboogie. thought these were aftermarket pistons like weisco.

  8. #8
    All hail the Chief! fullboogie's Avatar
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    Oh, no apologies needed. Didn't mean to be rude - I think we're talking about the same thing but just calling it something different.

  9. #9
    Altezza01's Avatar
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    mine makes a knocking noise when i turn it off. i dont know where it comes from. but my ski hasn't blown up yet...knock on wood

  10. #10
    banshee350racer's Avatar
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    I had Millennium Tech match the pistons to the cylinders so there would be no way that it could be piston slap. It is more like a Bang.........Bang. not a dink,dink,dink.

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