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  1. #1

    1994 SLT 750 PTO Burnout

    Hi everybody - if I'm posting in the wrong area let me know...

    Got a great deal on a ski and trailer, compression test found the PTO at zero - the other two over 120. Pulled the heads and snapped a few pictures. I've been reading up on the common issues and upgrades - looks like the stock fuel pump and lines. Based on these pics what do you guys think as far as my first line of action? Where and what would be a good first round of parts to buy until I can get going on tearing this thing apart? Great forum, lots of information - Thanks in advance!

    My boat is going in the water next week so I'm itching to get this thing running right before then. I can never seem to find time to do anything else once the season begins... I've got a boat with twins and had to pull one motor to start last year, hopefully this year its just this project
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    Last edited by hadvisor; 04-19-2014 at 10:06 PM.


  2. #2
    Click avatar for tech links/info, donation request K447's Avatar
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    Welcome

    if you have not already, look through my signature links for lots of useful info.

  3. #3
    ripcuda's Avatar
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    Welcome!
    See K447's signature link for all the details.

    You need to ditch the autocock, replace the single outlet fuel pump with a triple outlet, inspect/replace all the fuel lines, definitely rebuild the carbs (all three) with OEM Mikuni rebuild kits, make sure your carb jets and hi/low mixture screws (carbs) are correct for your machine, pull the jet pump and inspect the bearings/seals (rebuild if necessary), replace the seals on the thru-hull carrier...

    That's a good start!

    Cheers!

  4. #4
    So based on the attached would you guys think am ok to reuse the head and get a new piston (http://www.ebay.com/itm/Polaris-Piston-Ring-Set-750-SL-750-SLT-750-3240146-1992-1993-1994-1995-NEW-/321356831437?pt=Personal_Watercraft_Parts&hash=ite m4ad25c1acd&vxp=mtr), gaskets, updated fuel pump

    (http://www.ebay.com/itm/POLARIS-SL-SLT-SLX-650-750-MIKUNI-TRIPLE-OUTLET-FUEL-PUMP-CONVERSION-KIT-1992-95-/310919223186?pt=Personal_Watercraft_Parts&hash=ite m48643ad792&vxp=mtr, and carb kits

    fuel lines?
    http://www.ebay.com/itm/GENUINE-MIKUNI-SBN-CARB-CARBURETOR-REBUILD-KIT-POLARIS-SL650-SL750-SLT750-SLT780-/360485186064?pt=Personal_Watercraft_Parts&hash=ite m53ee976a10&vxp=mtr


    OR am I better off getting a complete top end kit and doing them all? Compression on the front two were both at 125..

    Do those links look like a good choice for parts? Would you recommend a different seller - site sponsor or or something like that?
    I got to the piston last night and couldn't get the clip out so I stopped there. Thanks for the input.
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  5. #5
    Click avatar for tech links/info, donation request K447's Avatar
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    John Zigler has always been an excellent source for Polaris carb rebuild kits, engine and other parts and customer support.

  6. #6
    dolson's Avatar
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    I have a 97 slt700. im going through rebuilding the top end as well. I am a Wisco dealer and can get you a top end kit if needed or use ebay. or you can use the SBT swap method. I didnt have the burn out pistion but the piston was pretty beat up like someone put a jar of bolts in the cylinder than turned the ski over for a coup hours. it was bad. Im not sure of the cause yet but working on rebuilding it.

    If the other two cylinders are at the same compersion as the third one will be I'd just do the one. If they are going to be uneven you should redo them all so they are the same. I think polaris is 125psi stock so you should be ok. You are not boring the cylinder correct, just replacing the piston? if you see problems with the other two then now is the time to do them but if everything looks ok then just do the one.

    idealy you want the cylinders all the same bore and same compression, some people will argue that you can just bore one it doesnt make a difference because it just a slight change. which probably is fine it probably will work, im not saying there wrong im just saying its not the ideal situation. Its all about the amount of money and effort you want to put into it vs how long will it last until you have to redo something that was incorrectly done.

  7. #7
    ripcuda's Avatar
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    I've bought two different Polaris skis... SL780 and SLT750... each had burned down one piston (usually the MAG). On each, the other two cylinders were clean with good compression. My skis are for recreation... not racing... so I went the affordable route in my rebuilds.

    I left the 2 good cylinders alone in both rebuilds. I pulled the piston and cylinder jug off the bad ones. In both cases I needed a new piston. In one case I needed a new head. And in the other case I needed a new cylinder. So I bought nice condition, used cylinder/head/piston combos and used what I needed. I then bought a set of new standard size rings for the used pistons. I lightly honed the jugs (ball hone) and put it back together with the used piston, new rings, new gaskets (base/head).

    Now that said. My two bad cylinders (on Fujis) were a broken ringland (tons of pot marks top of piston and head) and the other was a burned/overheated scorched piston scaring the cylinder walls. Your is a burn through (hole). In your case, there will be a considerable amount of aluminum debris in the lower end of your engine (under that bad cylinder). I had a Polaris domestic engine (1200) like that, so I fully disassembled the engine... splitting the cases... and was glad I did because of the tiny bits of piston down in the engine were everywhere in the crank bearings, etc.. Took a lot of flushing to get it clean and get the crap out of the main bearings. So how do you plan to flush out the lower crankcase area to get out the debris? Are you pulling the engine out of the ski... then on the bench, flip it upside down and try to clean it?

    Just some food for thought. I've heard of others just fixing the one cylinder, even on a holed piston... so I guess it's a gamble. Either way... you MUST rebuild the carbs, which are the very likely culprit for the damage (that and old single outlet pump... upgrade it). Otherwise... you'll hole out another one in short time.

    I like getting my new parts (rings) and carb kits from Zigler. I usually buy the used parts off forum members or ebay. That linked 3 outlet fuel pump is what I have on my 750... works great. You can also look for a pentagon-shaped triple outlet fuel pump that was stock on the 780's... then buy a $15 rebuild kit for the fuel pump (Zigler)... that'll work well too. Fuel lines... I inspect and if they are not hard, cracked (i.e. still pliable) and not all chewed up on the hose clamp ends (trim back if enough slack)... I reuse mine... or get new regular fuel lines from the auto parts store.

    Cheers!

  8. #8
    Quote Originally Posted by ripcuda View Post
    I've bought two different Polaris skis... SL780 and SLT750... each had burned down one piston (usually the MAG). On each, the other two cylinders were clean with good compression. My skis are for recreation... not racing... so I went the affordable route in my rebuilds.

    I left the 2 good cylinders alone in both rebuilds. I pulled the piston and cylinder jug off the bad ones. In both cases I needed a new piston. In one case I needed a new head. And in the other case I needed a new cylinder. So I bought nice condition, used cylinder/head/piston combos and used what I needed. I then bought a set of new standard size rings for the used pistons. I lightly honed the jugs (ball hone) and put it back together with the used piston, new rings, new gaskets (base/head).

    Now that said. My two bad cylinders (on Fujis) were a broken ringland (tons of pot marks top of piston and head) and the other was a burned/overheated scorched piston scaring the cylinder walls. Your is a burn through (hole). In your case, there will be a considerable amount of aluminum debris in the lower end of your engine (under that bad cylinder). I had a Polaris domestic engine (1200) like that, so I fully disassembled the engine... splitting the cases... and was glad I did because of the tiny bits of piston down in the engine were everywhere in the crank bearings, etc.. Took a lot of flushing to get it clean and get the crap out of the main bearings. So how do you plan to flush out the lower crankcase area to get out the debris? Are you pulling the engine out of the ski... then on the bench, flip it upside down and try to clean it?

    Just some food for thought. I've heard of others just fixing the one cylinder, even on a holed piston... so I guess it's a gamble. Either way... you MUST rebuild the carbs, which are the very likely culprit for the damage (that and old single outlet pump... upgrade it). Otherwise... you'll hole out another one in short time.

    I like getting my new parts (rings) and carb kits from Zigler. I usually buy the used parts off forum members or ebay. That linked 3 outlet fuel pump is what I have on my 750... works great. You can also look for a pentagon-shaped triple outlet fuel pump that was stock on the 780's... then buy a $15 rebuild kit for the fuel pump (Zigler)... that'll work well too. Fuel lines... I inspect and if they are not hard, cracked (i.e. still pliable) and not all chewed up on the hose clamp ends (trim back if enough slack)... I reuse mine... or get new regular fuel lines from the auto parts store.

    Cheers!
    This will also be a recreation ski that will be used sporadically. .
    I was hoping to clean up the cylinder, and order a new standard size piston and ring set and install the one with the motor still in.
    While in there upgrading the pump and rebuilding the carbs. Thats the plan at least, I know how things can change once it is torn apart. I'm not a huge fan of cutting corners but I really don't want to pull the motor unless I really have to.

  9. #9
    Well, all is about completed. Triple pump in, new piston/ring installed, carbs benched and built, block off kit installed, tank yanked and cleaned, new fuse for the display, cleaned shutoff switch, routed fuel lines..

    Couple questions. How should I prime this thing before I start it up? I really want fuel to be in the system as much as possible when I start the initial crank. I mounted the pump in the stock area and have the pulse line cut down as short as possible.( less than a foot long)

    When I had everything tore apart a saw that some of the reed corners were a bit chewed up. Budget was stopping me from replacing them right now. What kind of issues should I expect?

    Right now I have the oil level sensor zip tied up, what should I do to prevent the light to come on?

    Recommendations for initial startup?

    Don

  10. #10
    Click avatar for tech links/info, donation request K447's Avatar
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    If you disconnect the oil level sender wire inside the electrical box the oil warning should not appear. Just unplug the wire coming from the sender and tape it aside.

    An alternate method is to wire in a 33 ohm resistor in place of the sender wire. 33 ohms from MFD connection to ground will force a full reading on the display.

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