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  1. #1

    99 SLTH Top End Time (SBT Engine)

    Well, my SBT rebuild just failed and the 2-year warranty ended last month ! The first engine they sent me failed within 1 tank of gas. I know I know, many on the forums do not like SBT. However, I like my 99 SLTH and I want to move forward.

    Anyways, The MAG cyl/piston failed and I am getting ready to do open heart surgery. Something started to come apart because the MAG spark plug got dinged and closed the gap to zero. The plug is not mangled, it just barely got touched and closed the gap. I can see some scoring on the piston through the spark plug hole. I won't know the full story until I open her up.

    I am starting this thread to document what I find and what my options are. I have removed and replaced engines in a 94 sea-doo SPI (580 cc) and 99 Polaris SLTH 700 and went premix on both. Both times I used SBT engines, both times they failed within the brake in period. My sea-doo was done about 4 years ago and the second engine they sent me is still working.

    The Polaris didn't fair as well. So now I am thinking about a top end. Sometimes my questions can sound naive, please be patient with me.

    Can I do a top end with the engine in the hull?

    I hear it is very difficult to get the pistons back in the cylinders, any advice?

    When is a top end enough? how much damage can a top end fix?

    Thanks all.

    tj


  2. #2
    SPEED KILLS, BUT YOU GET THERE QUICKER Keddano's Avatar
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    Yes it can be done in the hull, Little harder but do able. Some take a piece of plastic cut from a milk jug and then tape around it to make like a ring compressor. Myself I don't and just cuss alot. The wrist pin snap rings are the bear on the red engines.

    If you don't find a cause,take a good look at the rod play, may have a Conn bearing going bad allowing the piston to extend into the plug. Then your looking at doing the lower also.

    Top end will only take care of Piston/cylinder wall/compression problems. At the gathering,we replaced 1 piston without removing the other 2 cylinders or even the exhaust pipe.

  3. #3
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    Other thing to look out for. I believe the SBT engines are all bored to 1mm oversize. You may have to resleeve the cylinders to use any other pistons, or just find some used cylinders that you can have bored.

  4. #4
    Rasta Mon Condoms We Be Jammin!!!!! TxVirageTx's Avatar
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    piston can't hit the plug and close the gap.the dome simply won't allow it.you've got a bearing coming apart and a piece got between the piston and plug.

    so 2 motor failures within the warranty and then a third outside the warranty.sounds exspensive.

  5. #5
    Thanks for the responses.

    If you don't find a cause,take a good look at the rod play, may have a Conn bearing going bad
    piston can't hit the plug and close the gap.the dome simply won't allow it.you've got a bearing coming apart and a piece got between the piston and plug.
    So far, just looking through the spark plug hole I can see scoring. I am thinking bearings or rings came apart.

    I believe the SBT engines are all bored to 1mm oversize.
    Yes the SBT engines are 1mm over.

    so 2 motor failures within the warranty and then a third outside the warranty.sounds exspensive.
    1 motor was on the sea-doo. The polaris went through 2 motors, 1 outside warranty. The sea-doo is running great, for now. Short of doing the complete build myself, I felt SBT was a good way to go. However, my disappointment with the first 2 engines and now this...............

    The first Polaris engine failed due to the front main bearing disintegrating. 1/3 of the bearings were gone, went throughout the engine. The sea-doo engine snagged a ring.

    I am going to the lake today to open her up. Thanks again for the inputs. I will try to get some pictures up.

  6. #6
    Well, I got a look today. Looks like the top ring is gone and beat up the piston and head. So far no signs of metal in the crank area.

    What is the best way to remove the piston? I got the 2 c-clips off. How do I get the pin out?
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  7. #7
    Here is a picture of the PTO piston
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  8. #8
    The head got beat up too, can I salvage it?
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  9. #9
    johnsonmtz's Avatar
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    Quote Originally Posted by tjruberg View Post
    Here is a picture of the PTO piston
    That's the problem right there.....you are extremely lean. The questions are:
    1) Is this a fuel delivery issue?
    2) Is there an air leak in the intake gaskets?
    3) Is there an air leak in the base gaskets?
    4) Are there air leaks in the font or rear crank seals.....or both?
    5) Are there air leaks in the case halves?

    If the engine is going lean due to any of reasons 3 through 5....shame on SBT. If it's #1 or #2 the problem is the fault of the installer. If the installer was you....well, tough lesson learned. I've done that once before, I didn't pay close attention to my carb settings after installing an SBT engine and scored the PTO piston from running lean.

    Your MAG piston got smokin' hot and melted.

    KJ

  10. #10
    She likes the bike. But the ski gets her wet!!!! xlint89's Avatar
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