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  1. #1

    Unhappy my slx 780 starts up but only gains half the rpms then bogs down when i give it gas.

    i have a 96 polaris slx 780 with only 59 hours on it..in great shape. was on the lake and one cylinder shit out on me... replace the cylinder and piston, has good compression. rebuilt the fuel pump for the heck of it to. it starts up, is getting oil and when i look in the carbs when its running and gasing it it seems to get plenty of gas. filled up the oil and gas so the gauges read full. changed the plugs... will only rev up to like half the rpms and bogs down. any suggestions?


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

    Did you rebuild the carburetors and clean them internally?

    Have the original fuel lines been replaced?

  3. #3
    yeah the original lines were replaced with black line. seems to be getting plenty of gas... was running excellent til i had a piston go on me. havent rebuilt the carbs...

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    Click avatar for tech links/info, donation request K447's Avatar
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    Quote Originally Posted by skeetur View Post
    ... was running excellent til i had a piston go on me. haven't rebuilt the carbs...
    Those two things are probably connected.

    Rebuild the carbs now.

    Check and clean everything in the fuel system, starting with the fuel tank. Clean the fuel selector valve, make sure everything in the fuel system is 100%.

  5. #5
    all that checks out..carbs are clean asa whistle... idles ok and revs to about 6000 ... half throttle then it just wont do anymore as i push the throttle...thinking its electrical. any other ideas?

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    Click avatar for tech links/info, donation request K447's Avatar
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    Quote Originally Posted by skeetur View Post
    ..carbs are clean as a whistle...
    Clean as a whistle looking down the carb throats, or clean internally after they have been opened up and inspected?

    Internally is where they need to be clean. Looking down the venturi throat doesn't count.

  7. #7
    i removed the plate of the side of them and is spotless, puller a jet out and had nothing on them , nice and clean. when running with the filter off i hit the gas and equal amounts of gas spray into each carb and seems to be plenty of gas. i mean i know you know alot more than i do about these. cant get it into a shop for like 3 weeks.. so long summer of jetski lol. i mean if your so sure about it being a fuel prob ill take the assembly off and look throguh them... just seems stragen was running perfect... blew a pistong ... fixed that and all of a sudden carbs arent producing...

  8. #8
    She likes the bike. But the ski gets her wet!!!! xlint89's Avatar
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    What happened to the piston? Did it get a hole in the center, or did the edge of it erode away?

    If it was either of those problems, you had fuel delivery issues to start with. That's what causes the piston to fail like that.

    REMOVE the carbs and THOROUGHLY clean/inspect them. There are filters on the back side that you did not see.

    Also make sure your in line filters are good if you have them. Inspect the water seperator for signs of a blockage. Inspect the petcock for the same.

  9. #9
    yeah the piston towards the rear eroded then blew a hole through it. i didnt see any inline filters but did clean the separator out which wasnt too bas but was a little brown in the bottom. i rebuilt the fuel pump. k i will take them off right now and clean the hell out of them and hope that helps.. do you know what the factory setting for the needles are.. how many turns out? i appreciate your help..its nice people do this for one another..

  10. #10
    She likes the bike. But the ski gets her wet!!!! xlint89's Avatar
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    Yep, fuel starvation on that cyl, or an air leak.

    That same brown junk in the water seperator is most likely clogging the carb's internal filters. Check that out.

    Then after you replace the damaged piston, do a leak down test to make sure the engine is sealed air tight. If not, air will get into the engine and lean out the mix. Same results will happen if you just replace a piston without fixing the cause of it failing.

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