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  1. #1

    Question Whats you opinion??

    i got a polaris 93 sl 750 and everyone is talking about holes in pistons and things like that i took the engine out and want to do it right with out any problems later on trying to get this done before may so i can go ride and play. not building a race ski just something to play and have fun so whats your opinion. i got a new fuel pump the triple outlet going to replace all the rubber hose and rebuild carbs wash out the fuel tank and replace the ngk plugs i have 7's may want to run 8's is there anything i should do? do i need to take the heads apart to check pistons and please let me know cause the ski ran just fine then we broke the drive shaft and it has sat for at least 5 years.. what to do what do not do i dont know


  2. #2
    She likes the bike. But the ski gets her wet!!!! xlint89's Avatar
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    Was the engine fogged/winterized for those 5 years it sat?

    What's the compression of the cyls?

  3. #3
    it was not fogged thats why i'm rebuilding the carbs the compression is 110-105-110 is that good?

  4. #4
    Click avatar for tech links/info, donation request K447's Avatar
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    Quote Originally Posted by freemandino25 View Post
    it was not fogged that's why I'm rebuilding the carbs
    That is not why you are rebuilding the carbs.
    You are rebuilding the carbs because they may be gummed up and clogged from age and old fuel.


    the compression is 110-105-110 is that good?
    You fog an engine to protect the steel crank case roller bearings (and the cylinders) from rusting.

    Without fogging oil sprayed through the engine before storage, there is a risk that the steel parts inside the engine have begun to rust. Even 'surface rust' in a roller bearing means it will not last long once the engine is running at full power.

    You can visually check the crank and bearings while you have the engine out.

    Hopefully you don't see any signs of brown rust, and all the bearings still turn smoothly, without any up and down play.

    Did you have all spark plugs out, and the throttle wide open, when checking compression?

  5. #5
    yes the plugs was out and wide open throttle when i checked for compression. so in order to check for rust does that mean i got to take the bottom end apart?

  6. #6
    Click avatar for tech links/info, donation request K447's Avatar
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    Quote Originally Posted by freemandino25 View Post
    ...in order to check for rust does that mean i got to take the bottom end apart?
    Depends how thorough you want to be.

    Removing the intake manifold and reed blocks will let you peer into the crank case. You can then rotate the crank and feel/listen/look for signs of rust or grittiness. You can use a light and a small mirror, but this is obviously easier if the engine is up on a work bench.

    The quick method is to remove the jet pump and drive shaft, then turn the PTO coupler by hand, and just go by feel. The crank should turn smoothly, with no connecting rod play when you reverse direction. If it seems good, then you can try running with it like that.

    If you are feeling really lucky, just clean up the carbs and fuel system, replace all the old oil and fuel hoses and filters, and run it

    Your compression numbers seem low, but they are reasonably closely matched. Again, some would suggest you remove the cylinders, check things over, and freshen up the top end (cylinder hone, new piston rings, etc).

    Others will say it seems good enough to run with for the time being. If the engine turns out to be low on power, then you can dig into it and renew things.

    With these old engines, there are very few certainties. You either completely pull the engine apart and rebuild, or you make a gamble whether some things may not be 100% good.

  7. #7
    She likes the bike. But the ski gets her wet!!!! xlint89's Avatar
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    Often you can get a decent look at the crank and rods through the intake opening where the reeds go.

    With the spark pluge removed, grab hold of the engine coupler and see if you feel any sticking, grinding, clicking as you turn the crank over by hand.

    If you don't see any surface rust, or feel anything questionable in the bearings, you should be OK to proceed.

  8. #8

    Question

    what if there is rust? can i take some scotch brite and shine the crank up? if i put new rings in the motor and hone the cylinders can i leave the bottom end or should i also do the bottom end i dont got alot of money but i dont want to just slam it together and have problems down the road from now so what to do? what is compression post to be and who hones cylinders around lewisville tx? can a car machine shop hone them and put cross hatchs in it. what do i do to the bottom end just re seal it? new rod bearing? i'm a car mechanic i work for a speed shop in euless building hot rod honda civics and engine transplanting so this is new to me on a jet ski? help me out guy thank you

  9. #9
    Click avatar for tech links/info, donation request K447's Avatar
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    If there is visible rust on the crank shaft, then there is probably also rust on the crank bearings (which you will not be able to see directly).

    Rusty crank roller bearings will not last for very long at high RPM - a few hours or a few minutes, maybe just seconds.

    If you inspect the crank, and you see rust, then the engine needs to come apart, and the crank shaft sent to a crank rebuilder who is familiar with Polaris cranks.

  10. #10
    She likes the bike. But the ski gets her wet!!!! xlint89's Avatar
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    Right ^^^^^^^^

    There's no way to install new bearings without disassembling the crank as it's press fit together.


    Hopefully there is no rust, but sitting that long without being fogged is questionable.

    It wouldn't be too hard to find a place that will hone cyls. Google a powersports repair shop in your area, they'll be able to inform you of who does their's. Should be about $10-15 a cyl.

    Really good compression on a warm engine would be around 120-130 psi. The engine will still run pretty good with 100 psi and up. You don't want more than 10% difference between any of the cyls.

    If you go into the bottom end, you will need to reseal it. Just a matter of using a silicone sealant gasket made for that purpose (3M 1211 or something similar) and new crank seals.

    Lots of info posted about this stuff already if you do a search for it.

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