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  1. #1

    Just Picked up some SLT 780's, need a bit of direction.

    So after pouring over the forum for the last few hours I have a few questions that I still don't have clarity on.

    Last week there were two SLT 780's in my area on craigslist that looked in good condition, and the people who owned them (for the past 6 years) were good "toy" people. AKA they fogged cylinders in the winter, trickle chargers between uses, kept them well covered, etc.

    The owners before last (Not me or the owners before me, but one set further back yet) had removed the oil injector pumps and went to pre-mix. 40:1 was the recommended ratio passed down.

    Pricing was more than fair so I bought them.

    Took them up to the lake and they fired right up, but they don't idle very well.

    Ran them on the lake for maybe 30 minutes and then put them back on the trailer as neither seems quite right.

    They take awhile to get on-plane, and once they do they don't go very fast.

    The one machine, looks stock other than pre-mix change, goes 27~29 and the other machine which seems to have a different pickup plate does maybe 40.

    Started researching and ended up back here.

    Seems like what I need to do from here is a few fold:

    1. Compression check and make sure my cylinders are within 110~120 psi. If not I need to investigate that further.
    2. Replace my fuel lines
    3. Check my impeller clearance (still a little unsure how I do this and if I need any special tools or not?)
    4. Rebuild my carbs.

    Does that sound right?

    Anything else I am missing or should look for?

    The Skis have about 300 hours on them and generally look like they have been well cared for.

    If everything looks ok, is there anything else which may be causing my performance issues?

    I'm quite mechanically proficient, but time can occasionally be in short supply. Is rebuilding the carbs a huge issue or not? Is it going to take days to rebuild the 6 of them?

    Thanks for all the help that you have given so far!

    Karl P


  2. #2
    Superd2K's Avatar
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    You're on the right track, but there are a few other things you should do. Here's where you start: http://polarispwcknowledge.shorturl.com/

    Rebuilding the carbs is relatively easy. Nothing to be afraid of. It can be done in a couple of hours per set. My first set of skis, I pretty much spent 2 hours in the garage for every hour I spent on the water. I knew absolutely NOTHING about them. This place is full of anything and everything you want to know about these skis. Go through that link, read thoroughly, search for topics relevant to what you need, then post away.

  3. #3
    BlueFishCrisis's Avatar
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    Welcome to the Hulk. Definitely rebuild the carbs. If you are mechanically inclined, should not be an issue. There are very few parts inside these things. The PWC knowledge link is invaluable for these skis, spend the time to read.

    I would also replace your fuel filters, clean out your gas tank, and rebuild your fuel pump. Kits can be had for around $20 and will ensure many more years of reliable operation to come.

    You will want 120+ of compression, but can live with less. Must be within 5-10% of each other as well.

    Check your carbs needle settings as well. Sounds like you may have a fuel issue with speed issues.

  4. #4
    Thanks for the recommendations, I had already gone through most of it, but I caught the manuals this go around which were very instructive.

    I realized with more work last night that I am looking for 120+ PSI thanks for the catch.

    I know this unit has a triple pump from the factory, but I haven't seemed to be able to find a rebuild kit?

    Additionally, It seems as though the best answer may be to just pop the cylinder heads and inspect both the pistons and cylinder walls.

    If I were to do this, what seals would I need? Obviously cylinder/head gaskets, but also some seals for the water rail? Anything else I am missing?

    Do you have to remove the entire air-filter box to get to the needle adjustments?

    Thanks!

    Karl P

  5. #5
    Sooo...how much for the 780? stimpsonjcat's Avatar
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    The top end needles are up under the airbox edge and hard to get at with it on. A ratcheting screwdriver will be your friend. Activate the choke when adjusting the tops and it gets the linkage out of the way better too.

    Does either have a functional display? If so is it blinking the red LED? Tried it with the displays removed?

    Most likely sounds like carb issues to me. What year are they? There were two different carb setups for the 780s and they use different settings on the screws. Count your turn ins when you take the carbs off and it should make it obvious which you have.

    Welcome to the 780 club, I have 4 now.

  6. #6
    BlueFishCrisis's Avatar
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    Fuel pump rebuild kit: http://www.ebay.com/itm/Genuine-OEM-...147a98&vxp=mtr John Zigler also has them.

    If you decide to take the heads off, you will need the gaskets for the water rail, and head gaskets. You will probably destroy the water rail gaskets during removal, but some members will reinstall the existing head gaskets after treating with copper gasket spray. If you do need replacement gaskets, I have some available.

    The needles may be adjustable without full removal of the FAs. I would at least remove the two bolts that hold the cover and element in place then go from there.......

  7. #7
    Thanks for all the info so far! So helpful.

    They are '97s

    Ratcheting screwdriver - check.

    They both have displays, one is in good condition (weathered but looks great), the other fair (display is dim across the bottom portion).

    I know they were blinking red when they first fired up, but I can't remember if it went away or not? I know that sounds bad but with pre-mix gas, functioning cooling, and displays (computers) of unknown quality and functionality I didn't pay that much attention to them. What does the blinking red mean?

    I did not try to take them off, how do you do that? Do you need to pull the MFD out of the handles?

    When I re-do the carbs, can they stay ganged together (I understand the fuel rail needs to come off) or do I need to break all the linkages between them?

    Furthermore, should I replace the needle jets/seats while i'm in there?

    Thanks!

    Karl P

  8. #8
    Sooo...how much for the 780? stimpsonjcat's Avatar
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    Quote Originally Posted by iamkarlp View Post
    Thanks for all the info so far! So helpful.

    They are '97s

    Ratcheting screwdriver - check.

    They both have displays, one is in good condition (weathered but looks great), the other fair (display is dim across the bottom portion).

    I know they were blinking red when they first fired up, but I can't remember if it went away or not? I know that sounds bad but with pre-mix gas, functioning cooling, and displays (computers) of unknown quality and functionality I didn't pay that much attention to them. What does the blinking red mean?
    They will blink for a few seconds when starting the engine, but should stop after that. If they are detecting any of several alarm conditions they will display that, blink the red light, and send a signal to retard the timing to protect the engine. BTW, if the display goes really dim you can (carefully) disassemble it and clean the connection between the LCD and the brainboard to get the digits back to spec. There are several good threads here on the procedure.

    I did not try to take them off, how do you do that? Do you need to pull the MFD out of the handles?
    It is pretty easy to remove them once you know the trick. Push a 6" blade flathead screwdriver up along the outer edge so it is in about an inch and a half and then pry outwards and the MFD will pop right out.

    When I re-do the carbs, can they stay ganged together (I understand the fuel rail needs to come off) or do I need to break all the linkages between them?
    Nope, they need to come apart, but if you do not adjust the syncing clamps then it is no big deal at reassembly time. Just pry the clamping pins apart and push the next carbs plate in, they will hold together well enough until you can get them started on the carb rail that holds them all.

    Furthermore, should I replace the needle jets/seats while i'm in there?
    Yes, get the rebuild kits from John at Watcon and you get new seats/valves with the other parts. Be sure to check the jets carefully, especially on any cylinders that look lean. I could see through one of my hi jets, but it was still gummed up.

  9. #9
    BlueFishCrisis's Avatar
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    The weathered MFD can easily be updated with a new face sticker available on ebay for under $10, if you care to do so.

    If you have faded LCD digits, those can be repaired as well, depending on how adventurous you care to get.

    The red light is used when running as a warning for Low Fuel, Oil, and high temp. It does flash when the start button is first pressed or when the mode button is pressed and the unit is asleep. The light should shut off if no other issues exist. The light should never be steady on.

    You will need to pull the handlebar pad off in order to remove the MFDs. There is a sequence outlined somewhere in the PWC knowledge link.

    In order to rebuild and clean the carbs, you will need to remove the back plates which is how the carbs are ganged together. The back plates do not need to be removed from the plate, but the linkages will need to be disconnected. You will want to re-sync your carbs anyway to ensure they are properly aligned.

    Get the carb rebuild kit from John Zigler. It includes only the parts you need, and at a very good price. They are genuine Mikuni and include the needles and seats. Remove and inspect the jets. If the taper has an dents or rings in it from being seated too tightly they will need to be replaced. The kit John has will contain the o rings you need for the needles, but not replacement needles if needed. He may have those available as well.

  10. #10
    Sooo...how much for the 780? stimpsonjcat's Avatar
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    Quote Originally Posted by BlueFishCrisis View Post
    You will need to pull the handlebar pad off in order to remove the MFDs. There is a sequence outlined somewhere in the PWC knowledge link.
    I don't take the pad off. Just use the screwdriver as described. Should I take some pics?

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