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  1. #1

    Polaris Project SL750 #15

    Why #15? I did a search in the project section for SL750 in the title and got 14 results so my project must be #15.

    A little background. 1995 SL750 that was running up to a couple of years ago. Was out with some friends and let the PWC sit for about 15 minutes and when I got back on it would not get above 4200 rpms. Thought that maybe I had water in the gas or just bad fuel flow. Drained gas and added 3 outlet fuel pump but had the same result. Now I am getting back to working on it.

    Tried to remove the carbs but 2 of the 6 nuts were so rusted that they stripped. My brother-in-law came over today to help me. I was still trying to remove just the carbs but he talked me into removing the whole engine. First time either of us had removed one from a PWC, and glad that I did!

    I looked inside the mag cylinder thru the exhaust port and saw that the piston was chewed up. Then I rotated the crank and noticed something missing. Yes, a big chunk of the skirt is gone! Don't know where it is, I'll have to check the water box again tomorrow to see if it is there but I didn't find anything yet. So I need to decide if it is worth while for me to rebuild the engine or just buy a remanufactured one and save myself a bunch of work. I hope the case is OK, or at least fixable.

    Anyway, the first carb nut came off with a little bit of effort. The second one was much more difficult. Finally got it off with a Dremel and a chisel at the expense of one of the carb studs.

    So, end of day 1 and the engine is out and the carbs are off. What is next? Get a price for a remanufacture engine with worst case options like supplying a new case (or fixing the existing one) and a new jug and head.
    Attached Thumbnails Attached Thumbnails Click image for larger version. 

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  2. #2
    Click avatar for tech links/info, donation request K447's Avatar
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    I expect the Fuji engine guys will suggest you tear further into the engine, so you have a better idea what your options are.

    If you only need to rebuild the one cylinder, the cost can be reasonable. Good used or re-bored cylinder, new piston kit, may be all you need.

    And of course the carb rebuild

    If the engine needs rebuilding/replacing, you have some options there too.

    Before you pull the heads off, check the crank index, per the service manual.

  3. #3
    I did check the crank index check with dial calipers per the service manual. Then I check it at .1" BTDC and .1" ATDC per a method I describe in another thread, perhaps I should put it here as well. From what I can tell the crank is aligned to within 1 degree, spec is 2 degrees. Now that I have it out out I can use an index wheel but I suspect the damage was from a bad crank bearing though I guess it could have been the piston bearing. Not sure what else would cause the skirt to break like that. If it is the crank brearing I am guessing $350 to rework it, does that sound reasonalble?

  4. #4
    Click avatar for tech links/info, donation request K447's Avatar
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    Quote Originally Posted by pseudonym View Post
    I...If it is the crank bearing I am guessing $350 to rework it, does that sound reasonable?
    Circa $400 is a number I have seen before. All depends on the crank shaft rebuilding shop you take or send it to.

    Jeff at Midwest crankshaft seems well regarded, but there are others that can also do a good job.

    The crank is a press fit design, so a press is used to pull the sections apart, and then re-assemble the crank with new bearings.

  5. #5
    I pulled the bearing housing and did a quick inspection and it doesn't look good. The manual says to inspect the bushings and seals in the assembly for wear or damage, no mention of bearings. Are there actually bearings in the assembly or just bushing?

  6. #6
    BBCaprice's Avatar
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    E-bay got lots of Polaris parts- new and used

  7. #7
    Click avatar for tech links/info, donation request K447's Avatar
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    Quote Originally Posted by pseudonym View Post
    I pulled the bearing housing and did a quick inspection and it doesn't look good. The manual says to inspect the bushings and seals in the assembly for wear or damage, no mention of bearings. Are there actually bearings in the assembly or just bushing?
    Which assembly?
    The through-hull assembly just has a brass bushing and seals.

    The impeller stator stub shaft has real bearings, and seals.

  8. #8
    The through-hull assembly. Good to know that it has brass bushings and not seized bearings. I'll do a thorough cleaning and see how it looks.

  9. #9
    She likes the bike. But the ski gets her wet!!!! xlint89's Avatar
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    Manual describes a cracked skirt can be caused by:

    excessive piston to cyl clearance

    foreign material in engine

    sharp ports

    modified engine

    or hydrolocked

    My guess is the skirt piece is in the case bottom. It's possible it's in the waterbox though....

    Open that baby up and see what you got.

    That will tell you if you can rebuild or replace.

  10. #10
    Took some electrical measurements today, all measurements are ohms:

    Stator Components
    Alternator Coil 0.6, 0.0% error
    Trigger Coil 217, 1.4% error
    Pulser Coil 86.4, 4.0% error
    Exciter Coil 487, 0.6% error
    Everything is within 10% specification

    Mag Ignition Coil
    Primary 0.2, 0.0% error
    Secondary 3300, 0.0% error
    Spark Plug Cap 5810, 16.2% error
    Spark plug cap is out of spec, everything else is within 10%

    Center Ignition Coil
    Primary 0.2, 0.0% error
    Secondary 3310, 0.3% error
    Spark Plug Cap 5040, 0.8% error
    Everything is within 10% specification

    PTO Ignition Coil
    Primary 0.2, 0.0% error
    Secondary 3260, 1.2% error
    Spark Plug Cap 4670, 6.6% error
    Everything is within 10% specification

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