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  1. #1

    Polaris sl 780 1996 restore

    Ok Im Very new to jetskis i'm 17 years old never driven one i'm quite a good mechanic and i learn and understand quickly I have a polaris sl 780 identical to this it has been 14 years in the garage never used. it was barely used just barely the exterior is just brand new it was my fathers jetski and he just stopped using it. I dont know how to get it started .
    Things i have done :
    - Uninstalled the fuel tank and drained the 14 year old fuel .
    - removed the jet pump and took to bore it since the tunnel shrinked some how and the prop inside doesnt rotate
    - removed the cooling manifoled
    - removed plugs and put some wd-40 on the cylinders and rotated the engine by hand
    - hooked up a new battry and tried to start it. starter works perfectly
    What should i do next?
    Thank you people in advance

  2. #2
    Superd2K's Avatar
    Join Date
    Jun 2009
    Boise, ID
    Probably the carbs. Or it could be the carbs But most's the carbs.

    Seriously, though. Here's where you start:

  3. #3
    Thank you that helps soso much

  4. #4
    Click avatar for tech links/info, donation request K447's Avatar
    Join Date
    Jul 2007
    near Toronto, Canada
    Quote Originally Posted by Polaris sl 780 View Post
    Thank you that helps soso much
    Welcome to the Hulk

    If the machine has been sitting untouched for 14 years then you should not assume ANYTHING is still good. Stuff may LOOK good on the outside but have issues on the inside.

    Age alone will harden, crack and degrade hoses, fuel lines, rubber and plastic parts. Grease can dry out and become useless, oils can drain away and allow steel parts to rust internally.

    It sounds like this machine may ave been used in salt water, if indeed the jet pump liner had bulged inwards and seized th impeller.

    In addition to all the stuff covered in my signature link below, consider these points;

    All fuel hoses should be replaced due to age. Fuel tank vent check valve(s) should be checked or replaced. Fuel filler neck check for cracking. Fuel filler cap check seal.

    Fuel tank level sensor float may no longer float, replacements are available.

    The carburetors absolutely need to be removed, taken apart, cleaned, and rebuilt using genuine OEM carburetor rebuild kits.

    Note that 1996 was the very first model year for the red 'domestic' Polaris engine. Polaris made a number of updates and revisions afterwards.

    One big change was the entire ignition system was found to be unreliable over time. Polaris issued an Ignition System Update Kit which replaces the original failure prone stator and also includes a new CDI module.

    Every water hose should be removed and checked for signs of age, cracking, or deterioration. Or just replace all the water hoses anyways.
    Open the thermostat housing and check for debris, corrosion, salt accumulation.

    Impeller stator bearings and seals should be replaced. The actual bearings inside the jet pump are steel and there is no way to be sure they are still completely unrated. When the engine is running at full power the entire drive line is spinning at over 6,000RPM. Even a 'little' rust inside a bearing will quickly result in a complete bearing failure at speed.

    The through-hull drive shaft seals are also liked dried out and in need of replacement. Not hard to do while you already have the jet pump removed.

    Now we get to the big question. Are the internal steel crankshaft bearings and piston wrist pin bearings inside your engine 100% non-rusted? Any rust at all means the engine either won't run at all or will have a short life at speed.

    It is difficult to properly check for bearing rust without tearing the engine apart. You can peer into the exhaust and air intake openings after removing the manifolds. If you see zero rust and a general coating of oil on the parts then the engine has a chance.

    Any signs of rust inside the engine means a full rebuild is likely.

    Even if the engine bearings are still good, the rubber crank shaft seals may be dried out and need replacement. Seal replacement requires the engine to be dis-assembled.
    Last edited by K447; 11-22-2012 at 11:08 PM.

  5. #5
    BlueFishCrisis's Avatar
    Join Date
    Aug 2011
    Medina, Ohio, United States
    All of K447s suggestions are very valid. Please confirm that you do indeed have an SL780 Blue Fuji Motor, not a Red Domestic. If you have the Blue Fuji motor, no need to worry about updating ignition systems.

    And, since you say you are new to jetskis, make sure you have the lanyard properly installed or the ski will not fire at all!!!

  6. #6
    Thank you very much for replying . Im pretty sure i have the Blue Fuji motor
    - the rubbers are in pretty good shape i must say the fuel hoses / water pipes dont show any signs of old age the are still very flexable and no cracks at all should i still change them?
    - The Impeller do you mean the proppeller if i can call it that inside the jet pump ? if yes i took it to a engineer and hes gona bore the tunnel and gonna make another type of metal called tylon i think not sure about the material.
    - What do you call that thing that was inside the fuel tank ? and where can i get a new one?
    - Im workig on removing the carbs i put the engine out sitting outside the ski im gonna take them apart tomorow do i need to buy a reuild kit ? the ski barely been used.
    - there was alot of oil in the crank case it was up to the exaust ports do you think rust can develop like that ? the engine is very easy to turn by hand.
    - how can i remove the engine wires from the electrical box without opening the box since i dont want to mess that thing up/
    Thank you very much for helping guys

  7. #7

    Join Date
    Aug 2012
    Brick Township, New Jersey, United States

    Polaris sl 780 1996 restore

    Yeah I'm almost positive you have the Fuji engine. All the hoses especially all fuel need to be replaced !! All carbs need to be rebuilt with genuine mikuni carb kits Good place to get them is here he is a friend of the forum and he has the kits with just the parts you need at the best price

    Even though they havnt been used that's actually worse for all the rubber gaskets in the carb have dried up and the fuel def varnished in there

  8. #8
    Is there a chart for the fuel / water plumming ? i get realy confused and i dont want to mess anything up Thanks for the link cascivic i will be buying stuff from there do they ship to malta ? island in the eu

  9. #9
    Which One for my ski please thank you.

  10. #10
    BlueFishCrisis's Avatar
    Join Date
    Aug 2011
    Medina, Ohio, United States
    RCJS-Polkit ......Rebuild kit for polaris fuji SBN38, covers all 3 carbs

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