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  1. #1
    johnsonmtz's Avatar
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    GRRR....something went south, and it wasn't for the winter

    Okay, so I didn't get to ride like I wanted to this year. We've had some prolonged warm weather so I decided this weekend to take the '96 SLT 780 on the lake for a short warm up run so I could fog the engine.

    Long story short, I made a couple of circles in the main basin and on the way back to the dock the engine lost RPM and died. It restarted kind of hard but it did get going. I popped the seat off and the PTO cylinder felt noticably hotter than the CEN or MAG. Anyway, I tried to run about 1/3 throttle but it died again but did restart. I thought "this can't be good" since I didn't see an overheat on the MFD, but i couldn't help but think that was the problem. There was all kinds of cornstalk trash floating all over the lake. When I saw all the stalk junk I had stopped and threw it in reverse hoping to clear the pump if I had sucked in some junk. When I finally got to the ramp I ran it up on the trailer and got it started enough to fog the engine. I figured if something was hosed I might as well make sure it's well covered in oil.

    I got home and immediately checked the compression. I had about 95psi on all 3 (this is an SBT motor so don't rag me on that). The MAG and CEN had thick, clear oil which is to be expected from the fogging. The PTO plug was covered in what looked like a pile of wet graphite . My guess is I'm looking at a top end job. I'll pull the domes at some point and post pics but for now I just wanted to share the sadness

    KJ


  2. #2
    warranty?

  3. #3
    SPEED KILLS, BUT YOU GET THERE QUICKER Keddano's Avatar
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    Hopefully it's something simple like a bad plug or coil that took a dump.

  4. #4
    johnsonmtz's Avatar
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    Zmann----you're funny

    Quote Originally Posted by ZMANN View Post
    warranty?
    I guess I should clarify, this is my 2nd SBT MOTOR. I bought the ski in early 2004. The previous owner had blown the OEM motor and had a local shop throw in the SBT reman just before I bought it. I ran that entire season and then the 2nd trip out in 2005 I lost an oil line on the CEN and things went clankety clank. I was about 4 months out of warranty so SBT said sorry. I wanted to get back on the water, so I just bought another SBT reman and installed it myself. This block is a little over 2 years old, so there's not a chance SBT will stand behind this thing.



    I'll pull the domes just to make sure the cylinders are okay. However, I can't help but think somethings gone bad since the PTO felt warmer AND the plug is covered with junk.



    KJ

  5. #5

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    gosh , i would say if you got 95 psi there is diffently something wrong ,

    but nothing new set of rings and hone job wont fix

  6. #6
    johnsonmtz's Avatar
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    Quote Originally Posted by 97sltx1050 View Post
    gosh , i would say if you got 95 psi there is diffently something wrong ,

    but nothing new set of rings and hone job wont fix
    So what kind of compression reading should I get? I thought I had seen that these Fuji motors shoudl be around 125psi, does that sound right?

    As I look back, I think I may have mixed the last tank of fuel at 50:1 Maybe I have scored things a bit and the PTO had a mild lean seizure. When I checked the compression earlier this summer they were setting around 105-110psi, so they are all 3 down a bit. But would a scored cylinder still show fair compression?
    KJ

  7. #7
    SPEED KILLS, BUT YOU GET THERE QUICKER Keddano's Avatar
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    Generally speaking as long as all the cyls are within 10% of each other you know the cyls are in about the same condition. With that said 95# I think would be considered on the low side,maybe needing a ring job.How many hours have been put on the new motor?

  8. #8
    race24x's Avatar
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    That sounds just like what my motor did when I broke a skirt off the piston. Same weird color and still had compression.

  9. #9
    johnsonmtz's Avatar
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    Quote Originally Posted by Keddano View Post
    Generally speaking as long as all the cyls are within 10% of each other you know the cyls are in about the same condition. With that said 95# I think would be considered on the low side,maybe needing a ring job.How many hours have been put on the new motor?
    I was aware of the 10% general rule, but I just wasn't sure what kind of target reading I should get. I don't know how many hours I've accumulated since 2005, but I wouldn't guess much more than 30. With 3 little ones running around, I just don't get time to ride much.


    Quote Originally Posted by race24X
    That sounds just like what my motor did when I broke a skirt off the piston. Same weird color and still had compression.
    Not exactly what I was wanting to hear, but kind of what I expected. Hopefulyl in the next couple of weeks I can pull the domes and get a first hand look.



    So the next question stands: Where's the best place to get a top end kit (piston brand, etc.)? Who should I send the jugs to if I need them machined? Am I right that a typical machine shop isn't the best place to use for these cylinders? If I can get away with honing I can catch up with a friend that has an extensive ball hone set.Since this is an SBT motor, I have no idea if these cylinders are oversized or OEM. For all I know they may be maxed out and I'll need to get new jugs.


    I guess it's only money!!!



    KJ

  10. #10
    Wankel till I die!! jonjonwells's Avatar
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    First off, you are definately not a max. There is lots of room to bore, that is unless there is major damage to the sleeve. As to who to send them to: Watcon, and Sharps are probably the most popular, but Hot Seat, Group K, and there are several others. These seem to be the most reputable guys around.

    I would have to agree that 95psi is way to low. I would at the very least hone and rering. You would be amazed at how much that will wake up an older engine.

    Pull that head. and post pics. While your at it pull all three.

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