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  1. #1
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    Needs choke to plane out

    I'm trying to fix all of the troubles with my newly bought GSXL -98 and this is the next in line.

    When riding the ski, it runs well on idle and up to about 1/4 of throttle. Above that it just dies on me, like there's no fuel. A temporary solution told to me by the previous owner is that if I hold the throttle at 1/4 and slowly pulls the choke until it starts to misfire and then squeeze the throttle slowly while letting off on the choke it will plane out like nothing. If I keep it planing I can go around for how long I want to, with different throttle positions. I can jump a wave and let of the throttle in air and give it full throttle after landning and it will still run great.

    The compression is 120/90, which of course is bad, but could this cause the above? Rebuild is planned to the winter and I want to sort out as many things as possible before that.

    Jetting is low 80, high 160, N&S 2.0 and spring I'm not sure. It's silver but I can't say if it's dull or shiny, it sure looks shiny to me. But it seems standard everywhere else so it should be a dull silver 95g spring.

    Low adjustment 2 out, high 0. I found that the standard setting should be 2 rotations out on the low adjuster in one workshop manual and 1 1/4 in another. What's correct here? And could this cause my problem?


  2. #2
    KrunchovXPL-GTX-RX's Avatar
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    LS adjuster should be from 1.5 to 1.25 turns out on a stock air box (which is pretty much the same for AM flame arrestors).

    It sounds like some one was chasing a lean condition (they probably would have opened the HS adjusters too if they could have gotten to them and pulled the limiter caps off). It is obviously still lean, considering the choke thing so somewhere in your fuel system you have a blockage. If it still has the gray fuel lines then it is due for new lines and a complete cleaning (switch and carbs both) and maybe a carb rebuild too.

    The compression would bear this out as that 90lb cylinder has likely suffered some damage (let me guess, that is the rear, no?).

    DO NOT RIDE IT anymore until that fuel system is cleaned out and the top end is fixed. If it has seized that low cylinder it will continue to seize at until the stress causes a bearing or the rod to fail. When this happens, it will be much, much more expensive to repair. If the piston has been holed, then it is liable to shatter (and I am sure the implications of a shattered piston at any RPM are obvious).

    At this point, should the crank prove to be sound, it will just need a top end and a good restoration of the fuel system. Ride it and you are risking damage/destruction some very expensive stuff (ie cases, carbs, starter, cylinder block, head, crank, CB shaft).

  3. #3
    If i knew,...I wouldn't ask sea-one's Avatar
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    You cant tune ANYTHING with compression like that.a maximum compression difference is 10 lbs.You'll be chasing every carb issue until you get the crankcase and manifold vacume pressures balanced...

    my 2 pennies

  4. #4
    KrunchovXPL-GTX-RX's Avatar
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    Quote Originally Posted by sea-one View Post
    You cant tune ANYTHING with compression like that.a maximum compression difference is 10 lbs.You'll be chasing every carb issue until you get the crankcase and manifold vacume pressures balanced...

    my 2 pennies
    True.
    That would be why it needs a top end. Well, that and the fact that it will eat itself. But if the carbs do not get fixed too it will be right back where it is a year from now.

  5. #5
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    Sorry, I was a bit unclear on the history of the ski as I know it and what I have done.

    The previous owner have used the ski like this for 2 years before me, using the choke to get it planing, and running it like that. I don't know why he hasn't tried to fix it, or maybe he has but not with success.

    The first thing I did about a week ago was to replace all the grey fuel lines, including pulse line and the tank vents. The fuel selector was stuck at the open position so I removed it and just put a T-piece instead of it. I also removed the carbs and cleaned them out thoroughly, but they were pretty clean even in the internal filters. The adjusters were turned almost like they are now, so I assumed that the 2 turns out on the low adjuster was correct. You can see that the high adjusters has been used quite a bit, there's no cap on them either. If I try to put the low adjuster at 1 1/4, it will be leaner right? And that's probably not what I want since it runs ok on idle and up to 1/4 throttle.

    Just have to mention that I was out riding it and pushing it quite hard with high revs and lots of full throttle a couple of days ago, and just of interest I removed my newly changed plugs to look at them. They were brown and nice, like the mixture is at least somewhere near correct at the revs and load I used it at.

    What circuit in the carbs are used above 1/4 throttle? Should I try to measure the pop-off pressure?

    Finally I understand your comments about it being hard to tune with the bad compression, and I believe that it has to do with this a lot as well.

    Thank you for your input so far!

  6. #6
    KrunchovXPL-GTX-RX's Avatar
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    Pop-off is not relevent at higher RPM. The N/S are pretty much open above a certain point and the only thing that matters then is the size of the N/S. The LS adjusters are only there to tune the idle quality. It should be boggy off idle and trying to load up at 2 turns out. The fact that it is not suggests that it is lean.

    Now, the boat is lean, and has been lean (as evidenced by the compression drop). The inlet screens are not the only things to clean in the carbs. You have to make sure the transfer passages are not clogged in the carb body and in the valve body that sits above the jets.

    In this case the nozzels for the accel pump may (probably are) clogged. But, it should still rev on up without the choke though it will be sluggish.

    As for the plugs. You can not read the color of the plugs unless you do a chop. As soon as you let it come back down to idle they will be dark again. The only way to read is to run it WOT for at least 7 seconds and while keeping the throttle open pull the lanyard. You need a long smooth stretch to do this correctly and safely as you must then pull the plugs to read them without starting the engine again.

    Now, in the case of this boat I would not risk doing any WOT runs. In fact, I would not even start it again before that top end was fixed.

    If the fact that the PO rode it lean as hell for two years makes you feel better about it then we will just have to disagree. People whistle past the graveyard all the time but when your number is pulled...it is time to go.

    Just how, exactly, did you plug in the "T" fitting when you removed the tank selector valve? All you would really need is a splicer to allow you to hook directly between the hose to the filter and the "Reserve" hose. Then block off the "On" hose.

  7. #7
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    I cleaned everything out in the carbs except the accel pump which I cleaned yesterday(totally clogged), not testing it after that. Took out the jets and blew through with carb cleaner in every hole I could find. I tried to follow the great "clean you fuel system" thread point by point.

    I'll probably take my chances with at least testing different low adjuster settings, I'm curious if the cleaning of the accel pump made any difference as well. As for WOT runs I'll probably take it easy if I don't find any obvious reasons to the weak spot I have.

    Regarding the fuel valve, I just removed the valve and connected all three loose ends to a T-connection. Obviously I won't be able to use the reserve capability since there will be air entering through the on hose when below that level. But I'm running with almost full tank so there shouldn't be any problem right?

  8. #8
    KrunchovXPL-GTX-RX's Avatar
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    Quote Originally Posted by Sandell View Post
    I cleaned everything out in the carbs except the accel pump which I cleaned yesterday(totally clogged), not testing it after that. Took out the jets and blew through with carb cleaner in every hole I could find. I tried to follow the great "clean you fuel system" thread point by point.

    I'll probably take my chances with at least testing different low adjuster settings, I'm curious if the cleaning of the accel pump made any difference as well. As for WOT runs I'll probably take it easy if I don't find any obvious reasons to the weak spot I have.

    Regarding the fuel valve, I just removed the valve and connected all three loose ends to a T-connection. Obviously I won't be able to use the reserve capability since there will be air entering through the on hose when below that level. But I'm running with almost full tank so there shouldn't be any problem right?
    Good, you are doing ok then

    It should still accelerate even without the pump squirting, it would just be boggy and would not need the choke.

    Does it still have the stock air box on it?

  9. #9
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    Yes, the standard air box is still on it. (Which makes it a pain to access the high speed adjusters )

  10. #10
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    Quote Originally Posted by KrunchovXPL-GTX-RX View Post
    Good, you are doing ok then

    It should still accelerate even without the pump squirting, it would just be boggy and would not need the choke.

    Does it still have the stock air box on it?
    It will accelerate, but be very, very tempermental to get it there. With the pump clogged, it will fall on it's face more easily than try to rev. They jet it lean on purpose to get emissions, so when the pump isn't there to compensate it will run like crap.

    God job following the DIY fuel thread!

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