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  1. #1

    2001 LS2000 rough motor

    Hi everyone, My name is Shawn out of Long Island NY. This is my first jet boat and unfortunately already have some issues the previous owner didnít make me aware of. I was hoping some of you can give me some friendly advise




    Boats history
    - GP1200 65Uís
    - Carbs rebuilt
    - compression around 110 on all cylinders both motors
    - oil pump removed, mixed fuel
    -Electric Fuel Pump I staled K group
    -New flywheel
    • stator


    So when I first bought the boat I bought it with a blown fly wheel on the motor on the passenger side. When I removed the bad flywheel I found the rear crank case gasket to be in pieces. I was under the assumption that this would have caused the rear cylinder to have low compression. I went ahead and replaced the rear seal and found the compression on cylinder #3 to still be low. At this point I decided to go ahead and remove the top end and found piston #3 to have a scores and head damage. The other two pistons were free of scores and damage. I decided to just replace the one piston as the others seemed to recently been replaced. (May have not been the best idea) while I had the top end off I decided to also rebuild all 3 carbs OEM parts since they were leaking on the fuel side? ( other side of where the seat and spring were) (I did not replace seat or needles just o rings) still currently 1.2 with a pop off of 55 PSI.
    I installed everything back together and am getting around 110 psi across the board (still under spec)


    I set the carbs to be 1 turn for low and #1 & #3 at 1 turn and #2 3/4 for
    High side


    Now when I go to crank over the passenger motor it wonít start without starter fluid and it will run very rough then start to make a Rev limiter sound.




    The driver side motor had 110 PSI compression but was also hogging out. I found clyinder #3 to be getting no spark. Currently waiting for a wire to come in.


    Please see below videos for current idle sound of motor. It sounds extremely rough.


    Also please note
    • spark plugs are all brand new









  2. #2
    raiderteen's Avatar
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    I'm guessing you haven't been around 2 stroke skis either? That last video sounds for the most part perfectly fine to me.

    Few things to remember.

    Out of the water characteristics...

    When running out of water these are going to idle around 3k rpm. Reason being is there isn't any load on the impeller when not in water. So the engine is just free revving. In water idle should be set at 1500ish rpm. This results in a 3000ish rpm idle when running out of the water. If the idle adjustment is set higher than that it will red line very easily/quickly when throttled up and be somewhat slow to return to idle rpms.

    Second thing.

    These engines are loud. They are very loud out of the water. They are even louder yet when idling away at 3000rpm due to the above reasons.

    Third thing. (Really important)

    When running on the hose ALWAYS follow the following procedure. Start the engine first. Then turn on water. Then when finished turn the water off FIRST. Then shut the engine off. Reason being, the water being on while the engine is off will fill the exhaust system up and eventually back flow into the cylinders flooding your engine. You can run these for 15 seconds or so without water without causing damage. The goal is to not get the cylinders/pistons too hot.

  3. #3
    I am fairly new to two stroke motors. My concern is when I rev it (out of water) it sounds like it’s bogging out. Is this normal? When I had skis it would
    make more of a zing noise.

    also mind you In the video I was running with no air intake. Would this cause it to run lean?

  4. #4
    raiderteen's Avatar
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    If it is bogging out of the water it will definitely bog in the water. The air intake not being on can cause a lean bog do to the change in air flow/signal through the carb throats.

  5. #5
    Raidertenn,

    Do you think that's all that can be causing the bogging?

    Carbs have all been rebuild with a pop off pressure of 55 PSI on stock 1.2 seat and needle ( I just ordered some new 95g springs to get my pop off pressure up to 75-80 PSI per stock spec)

  6. #6
    raiderteen's Avatar
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    Quote Originally Posted by smceniry View Post
    Raidertenn,

    Do you think that's all that can be causing the bogging?

    Carbs have all been rebuild with a pop off pressure of 55 PSI on stock 1.2 seat and needle ( I just ordered some new 95g springs to get my pop off pressure up to 75-80 PSI per stock spec)
    When I rebuilt my LS2000 carbs I was very happy with the results I got from following Group Ks suggestion which was running the 115g springs. I brought the low speed adjusters out 1/4 turn from factory to compensate. Reason I did this is I have a long cove that is all no-wake zone. Our normal place we tie up with friends is at the mouth of the cove and the lake house is in the back of the cove. Some days I will go back and forth a couple times ferrying people around before ever getting out of the no wake zone and opening it up. I see no "load up" symptoms when I eventually hit the throttles to take off. Idle is great and as smooth as can be expected for these triples. Granted I also run the oil injection so I am not over-oiling at idle and loading up from oil either.

    You shouldn't see any bog when revving on the trailer. That is the most responsive the engines will get due to the lack of water loading the engine. Try tossing the air box back on it and see what happens. But then again if you have a pop off of 55 with the 1.2 seats then I am guessing you have 80g springs installed? Factory is indeed the 95g springs. And as mentioned above 115g springs will work as well with a slight turn out on the low speed adjusters.

  7. #7
    Thanks for the information hmmm. I shall give this a try today and get back to you.

    Thanks Raiderteen, Thank you for the advise and help. Ill post a video of the results

  8. #8
    Went ahead and installed the air filter. No change at all. Still bogs when revving up.
    the only thing that’s not up to stock spec is the pop off. Can this really cause the engine to act this way or should I be looking at something else other than the carb?

    there was this one gasket that was behind the fly wheel when I changed it that had damage. See photo. Is this associated with the crank case? Maybe I have a leak? or when I changed the stator(broken fly wheel damaged) I messed up timing?
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