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  1. #1

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    Newbie with dropped cyl.

    Working on a friends pair of 750 slt's. One has 120,120, 0 psi rear. The other has 118,0,115 rear. They ran fine at the end of the year last year then they sat till last month. They would not rev out so i did the comp. check. Before i take the heads off, are pistons rings and gaskets still availble for this ? Should i just hone and re ring and go with it ? Looked at this site for hours it seems and just looking for a direction to go. I have done full engine rebuilds on my yz 250 including crank but three cyl. is new to me. LOL. Awsome site and thanks in advance. Greg


  2. #2
    burtonrider10022's Avatar
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    Quote Originally Posted by Two750slt's View Post
    Working on a friends pair of 750 slt's. One has 120,120, 0 psi rear. The other has 118,0,115 rear. They ran fine at the end of the year last year then they sat till last month. They would not rev out so i did the comp. check.
    Are you POSITIVE they were running fine? Or were you just used to the poor performance?

    Before i take the heads off, are pistons rings and gaskets still availble for this ?
    Yes. WSM seems to be the prefered choice around here. ~$80 per cyl. on eBay, cheaper through some vendors here. I believe Atlantic JetSports had the lowest price I've seen yet...

    Should i just hone and re ring and go with it ?
    Fixing the aftermath won't fix the cause, and it will just detonate again, quickly. Go here: http://polarispwcknowledge.shorturl.com/ and look at the fuel line and pump issues that should be corrected with the repair. I'm pretty sure all 750's are Fuji motors, but what year(s) are the skis? A good carb cleaning wouldn't be a bad idea either. Hone & ring will depend on cylinder wall condition, you may need a small bore.

    Looked at this site for hours it seems and just looking for a direction to go. I have done full engine rebuilds on my yz 250 including crank but three cyl. is new to me. LOL. Awsome site and thanks in advance. Greg
    I've browsed this site for way too many hours already. I'm sure someone more knowledgable will chime in about your original issues, but that link above will most likely answer any, and all, of your questions.

  3. #3

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    The ski's are 1995's and they did run pretty good except one had a small hesitation off bottom. Im aware of the fuel line's and filters replacement and the tripple outlet pump , auto cock , and cleaning the selector valve . I think he ran them with old fuel in the tank. Thanks for the reply !!

  4. #4
    Sooo...how much for the 780? stimpsonjcat's Avatar
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    When you do pull the heads, get pics. I am discovering that it is usually pretty obvious which cylinder needs PARTICULAR attention when cleaning carbs etc. Piston wash is an amazing diagnostic.

    And the folks here can usually ascertain the level of damage to cylinder walls pretty accurately based on piston wash and damage. With 0 PSI cylinders, it's going to be pretty obvious damage I am betting.

  5. #5

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    OK i have the first ski tore down and it had a hole in the top of the rear piston. Cyl. don't look to bad and should clean up and i did not see a std. stamp on the other pistons but did see W7A on the top. I have'nt got a manual yet so do i need a T guage and micrometer to measure or is this stock ? Does anyone know if Gates 1/4 '' hose number 4219N fuel line is OEM to the ski or has some one changed it already ? Connecting rod feels good vertically and has 18 thou. side play. Any thing else i should be concerned with ? Thanks in adv.

  6. #6
    I'm addicted to Polaris PWC ghostinstallations's Avatar
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    Gates is replacement. The lines would say TEMPO and be a obvious gray color if they were stock.

  7. #7
    Sooo...how much for the 780? stimpsonjcat's Avatar
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    It's funny that a hole in a piston center is sort of a good thing.

    Do check for bits and pieces down in the crank!

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