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  1. #1

    Join Date
    Apr 2014
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    Garland Tx
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    Lightbulb '96 SL780 Rebuild and Broken Crank Case

    Hi Everyone, I've been lurking around the polaris section for about a year, AMAZING posts, tons of really good info. So I thought I would share my little project. I got deal on a '96 SL780 that had good compression but no spark and occasionally no starter to bendix engagement.

    I drained and pulled the gas tank, opened the Mag end to find water had entered the Mag case. Further inspection inspection revealed much more damage. The lower half of the crank case had been previously broken and JB welded. The break in the lower case also stripped out a bolt hole in the upper case.

    I just ordered a nice lower and upper crank case from ebay (got lucky, from a 96 SL780 and $48 with free shipping)

    There's already Ton of good threads on Rebuilds so I thought I would show This.

    Here's Photos of the Broken crank case.
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  2. #2
    Click avatar for tech links/info, donation request K447's Avatar
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    Inspect the replacement crankcase carefully. Examine the bearing support areas for unevenness or pitting/damage.

    The crankshaft requires the bearing supports to be perfectly aligned and fully supporting the bearings, otherwise the crank can sag or shift around as the engine runs, which is not what you want.

  3. #3

    Join Date
    Apr 2014
    Location
    Garland Tx
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    23
    Damn good advice K447. I have high hopes, but realize this could end up bad. Between the great rebuild thread and the Beerdart PDF I feel confident.

    I did carb rebuilds and updates last year to my 92 SL650. Adjusting carb jets for a modified arrestor was seriously hard. I'm painting my SL650, I'll post about that some time.

    I know the Fuji motor isn't perfect, but I like 'em.

    If anyone wants different angles of pictures just ask.

  4. #4

    Join Date
    Aug 2014
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    Richardson, Tx
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    Don't sell that Fuji short, that 780 will run very strong and reliably for a long time if rebuilt correctly. You are in a great position to update that ski to SLX specifications and pick up a good chunk of performance. I live in Richardson, I do have some OP FA's I would sell very reasonably if you are interested. I can even deliver to Garland.

  5. #5

    Join Date
    Apr 2014
    Location
    Garland Tx
    Posts
    23
    This sounds stupid, but your talking Ocean Pro Flame Arrester? I'm totally interested. PM me, I'm right on the Garland Richardson border

    I didn't think there was alot of performance mods, so I didn't really look.

  6. #6

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    Apr 2014
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    Garland Tx
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    23
    Here's a few more pics.
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  7. #7
    BlueFishCrisis's Avatar
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    The crank might not be in such good shape if all that water got in.....

    That looks like an aftermarket bendix too...... Just an observation.

    You probably won't find much advantage to the Ocean Pro FAs over the stock 780 one as there isn't much of an airflow difference in my opinion. In fact, I find the OP FAs a bit more of a hassle when it comes time to take the covers off and tune as you have to remove 9 nuts vs 2 bolts with the stocker.....

  8. #8
    john zigler's Avatar
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    Just a FYI when the time comes, I have new pistons, rings, can bore your cyls to match, also have gaskets, crank seals, case sealer, etc.

    Have genuine Mikuni brand carb rebuild kits, fuel pump rebuild kits, and more.

    Good luck with your project. You will really like the 780 when you are done. Great little ski

  9. +1 by:


  10. #9
    Banned User
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    The 780s are great motors. Nice power and torque from a small cc engine. Keep the fuel system clean and they will run a long time.

    Mechanically, all of the Polaris motors are really good. Polaris had fuel system issues with the blue motors and ignition/electrical issues with the red motors. All well known issues, and once corrected I have found the Polaris machines to be very reliable. Any ski, especially an older one, will only be as reliable as YOU make it.

  11. #10

    Join Date
    Apr 2014
    Location
    Garland Tx
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    The Crank case is ordered, and in the mail, I'm hoping the water by the Mag was superficial, we shall see. Might get lucky.

    Super thanks for all the info guys, greenhulk and you folks seem to be the best resource for our discontinued skis.

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