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  1. #1

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    97 STX 1100 carbs issue

    Hello and thanks in advance for the help

    i purchased two stx 1100s that have sat for years. After getting the carbs cleaned by a shop ( and paying a good amount of money) it ran great for a hour. 55 on the river no problem.

    Then a guy on a boat ran out of gas and I towed him to a station for about 20 minutes slow. After my ski ran up to 55 then bogged down. I shut my ski off to check things. Nothing was overheating. Started it back up and then it wouldn’t go more than 20. Then slowly it got down to 10. Thinking it went into limp mode I was slowly making my way back to camp and it suddenly picked up and hit 40 when I was holding half throttle. Thinking it was ok I give it some more gas and it instantly bogged down to a crawl. Now it’s almost impossible to go more than 10 mph.

    After fighting my way up river for over a hour it would randomly pick up and then bogged. Changed its speed more than a moody child.

    i really don’t want to go pay another 500 bucks for my carbs to get worked on just to have this same situation arise latter. Does anybody have a thought on what it could be. I know dirt bikes very well but ski carbs are very foreign to me.

    Thanks again


  2. #2
    Once you understand the differences in carbs they are pretty much the same. PWC don't have a gas tank above the carbs so they use a fuel pump. This is on the carb itself and is just a diaphragm that operate off the crank case pulses. The fuel pump pumps the fuel across the carb to where you would normally find a float bowl. Normally Floats would meter fuel up into the jets EDIT float meters fuel into the bowl. With a fuel pump pressures are much higher so the float is replaced with a spring. The spring holds the needled down until the pressure "pops" the needle open to fill the reservoir the jets consume.

    Does the ski pull rpms out of water? Check the battery cables and grounds. Put in new plugs and ride around and check color.
    Last edited by Hishman; 05-20-2019 at 04:07 PM.

  3. #3

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    Thats great info on the carbs, thank you!

    When I pulled it out of the river and throttled it to clear water it did rev up easily while not under a load. The plug in cylinder 1 was fouled, I replaced it while I was on the water but it didn't make a difference. Ill check all the cables tonight. Would a loose cable cause these kinds of issues? Everything was powering on and off just fine and I never had a issue starting.

  4. #4
    If you found a single fowled plug it is potentially an issue with that carb or an issue with that spark. Since the carbs were just gone through I might look at the plug/coil first. Unplug the coil for that cylinder and clean up the connector and apply di-electric grease. I'm more familiar with seadoos but I don't think the wire is serviceable so you can't trim back the plug wire. If that doesn't work I'd just order a new coil since they are pretty cheap. It never hurts to have a spare anyway.

    If you have strong spark the only other thing that would cause a fowled plug is too much fuel or less likely oil deliver

    Before you do any of this replace all the plugs and confirm that that one cylinder is fowling up after riding.

  5. #5
    Rodsatheart's Avatar
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    Prob. just the plugs. Replace all of them. These things don't like to be run at low throttle for extended periods of time, and if that's going to be the norm, you might consider going to a hotter plug.
    Yes the wires can be trimmed and even replaced with solid core wire. Trimming 1/2" is common.

  6. #6

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    Quote Originally Posted by Rodsatheart View Post
    Prob. just the plugs. Replace all of them. These things don't like to be run at low throttle for extended periods of time, and if that's going to be the norm, you might consider going to a hotter plug.
    Yes the wires can be trimmed and even replaced with solid core wire. Trimming 1/2" is common.
    Thanks!

    I was thinking about that yesterday. My two stroke dirt bikes hate life when my friends ride it slow around the desert. Pulling that boat could have messed them all up.

  7. #7
    Myself's Avatar
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    Yes, plugs first. Anytime I've towed a boat for somebody farther than 1/2 mile I fouled plugs.


  8. #8
    Quote Originally Posted by Hishman View Post
    Normally Floats would meter fuel up into the jets EDIT float meters fuel into the bowl. With a fuel pump pressures are much higher so the
    float is replaced with a spring. The spring holds the needled down until the pressure "pops" the needle open to fill the reservoir the
    jets consume.
    That is a misconception. The seat doesn't open because of pop-off pressure.
    It opens because atmospheric pressure pushes it open, with help from manifold
    and or ported vacuum. That is why vacuum leaks are a common problem.

    The max fuel pressure is ~7.5 psi or nearly the same as the average crank
    case pressure. A 30cc weed whacker produces the same peak fuel pressure
    as the 1100. Only the volume is different.


    Bill M.

    With the exception of how the needle and seat opens, a regular carb functions
    much the same as a watercraft carb.
    Last edited by wmazz; 05-25-2019 at 06:52 PM.

  9. #9

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    Ok so.

    I changed the plugs. Ski ran great for a hour 55 mph. Then after a hour it started having issues. So I changed the plugs out again on the water but nothing changed. Still acting up.

    We sat for a while and talked. Then she ran great for about 5 min and back to the bog.

    I’m out of ideas. Lol

  10. #10
    Myself's Avatar
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    Sounds like a no spark on one cylinder.
    There are a couple common issues I find on these old triples. First check all coils. You can ohm from the boot to ground (around 10k ohm) and ohm at the coil connector in the box (around 1 ohm). The actual coils don't go bad often but the plug boots go open and the plug wires can break internally. Wiggle them around while ohming. Next common issue I find is corroded coil connectors that don't make good contact. Sometimes you can get them clean and pry the little contact tabs out so they connect tighter. Other times I cut them off and crimp on bullet connectors. If everything there checks out try swapping a coil connector and see if the no spark follows the connector at the cdi. If it does, then there is a cdi fault. Not near as common as bad coils or finicky corroded coil connectors.

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