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  1. #1

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    need some help on a 1998 seadoo gtx ltd

    hey guys a couple years ago my fiances seadoo gsx ltd cracked the rear piston and toasted the topend. i got out the sport for a couple years due to school and stuff and sold both of my skis so now i am looking to rebuild this one. they had it worked on a couple days before. and i think the oil injection is what went out. my question is i should be safe with just a bore over and top end rebuild? i will take the oil injection off and i will need a new head for it. also how should i go about checking the rave valves... thanks guys

    this is going to be my first seadoo rebuild but i have done a few yamahas polaris and tigersharks.


  2. #2
    KrunchovXPL-GTX-RX's Avatar
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    Just FYI, the oil injection hardly ever goes out.

    '98s came from SD with a gray tempo fuel line that has a rather disapointing tendancy to come apart on the inside and in the process clog the fuel inlet screens, fuel valves, and just about anything else in the fuel system.

    This generally results in a lean condition to which the rear cylinder is the more vulnerable since fuel is delivered to the front carb first.

    A couple of years ago those lines would have been 10 years old if they had not been changed at some point.

    Loss of lube does happen though. Mostly you see cases where injection oil brands were mixed in the tank resulting in a gel like goo clogging up the oil filter, or an injection line cracked, or was damaged during maintenance and not noticed and repaired due to negligance. In those cases you tend to see damage to all of the affected cylinders (ie, if the line to the front was damaged, bad front cylinder, good rear or blocked filter, both). A loss of lube failure tends to leave you with badly scored pistons that look kind of like course sand was dumped into the engine while it was running.

    Perhaps you can take some pics and we might be able to help you ID the problem before you get rid of one of the most reliable systems SD and Rotax ever used.

  3. #3

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    thanks for the reply with this yea i see what your saying it scared the crap out of the rear cylinder and it does still have the grey fuel lines on the bike and i heard about this in the past but never thought about it. so they will get changed asap. also the front cylinder looked good like i said the rear was cracked the rod was moving around in there so i will pull the jugs and see if the rod is bent. i really hope it is not also. they had a mechanic work on it a couple days before it broke and he fixed a leak on the oil tank so i am going to remove the lines and replace them and check the oil injection to make sure.

    looks like my plan of attack will be an overbore with a top end kit prolly going to have to go .5mm over. i am going to have the head resurfaced got a couple knicks in the rear dome. pull old fuel lines off and new fuel lines. and pray really really hard that the rear rod is not bent.

  4. #4
    canuck's Avatar
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    When you do the fuel lines pull the carbs and give them a good clean with fresh rebuild kits, check the fuel selector for blockage and the condition of the strainer under the front hood. This would also be a good time to get rid of the factory airbox and install flame arresters and rejet the carbs.

    You should post up some pics of the cylinders as the guys here are pretty good at helping you figure out what caused the damage.

    When they are running correctly the 951 is very reliable with some minor ongoing maintenance.

    I have the same ski and even though it's over ten years old I still enjoy riding it, it's decently fast, handles the chop good and will tow almost anything and anyone I hook to it.

  5. #5
    KrunchovXPL-GTX-RX's Avatar
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    The '98 GTXL is a fine machine and a good looking one too.

    When you say the piston cracked, do you mean, perhaps, that a chuck was broken off the top?

    If so, was this right in line with the exhaust port?

  6. #6

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    i dont remember exactly i will be getting it to my house soon to take down but i think it cracked inline with the intake and exhaust. i know the rod is disconnected from the bottom of it and it had a few chunks sitting around on top. i guess i will have to go through the rave valves to then huh?

    also found out that the carbs were rebuilt right before this happen by the same mechanic.

  7. #7
    KrunchovXPL-GTX-RX's Avatar
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    The exhaust port is the one that matters.

    On a 2-stroke the intake ports are actually the ones where the carbs (or manifold, if a single carb) connects to the cases.

    The ports leading into the cylinder are called the Transfer Ports (with two extra ones at a slightly different level in the cylinder called Boost Ports). The transfer ports pretty much circle the cylinder and the boost ports are opposite the exhaust port.

    What may have happened is that while it was running lean (perhaps the reason the carbs had to be rebuilt) the rear piston was running a bit too hot. There is a small pin in the ring groove that keeps the ring from spinning (if the gap gets into a port one or both ends of the ring will spring out, with catastrophic results). That pin is made of steel and will absorb heat at a different rate than the aluminum of the piston.

    If the pin gets hot enough it can melt into the piston. This can result in a hole in the side of the piston but it can also allow the ring to start to spin. Then it is a race to see what kills the engine first, a hole in the side of the piston, or a ring opening into the exhaust port.

  8. #8

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    personally i think the mechanic that did the work on it is the reason why it is broken now. they brought it to him and said service it and he told them i am going to do all these things and then 30 min of run time and its dead. i understand how the ports are on the regular 2 stroke motors i have had exactly what your talking about happen ot my polaris hurricane. it is understanding these rave valves that i am confused they are on the exhaust side correct. but how do they work?

    also your fuel line thing seems to be a very reasonable answer considering he was playing with the oil tank when it was worked on and the ski still has the grey lines on it. i cant wait till i finish my boat so i can bring this thing in the shop and tear into it and really see what caused the failure.

  9. #9

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    just talked to my father in law he said the bill says the fuel lines were replaced is it a good possibility the oil lines were never blead back and were just full of air and thats what caused it to burn the top end on the rear cylinder.

  10. #10
    KrunchovXPL-GTX-RX's Avatar
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    Take a look at the sticky about fuel system cleaning. There is more to it than just replacing the lines. Keep in mind that 10 years down the road may have been too late for it to matter. Closing the barn door, if you will.

    If the main feed line from the oil tank had air in it most, if not all of it will bleed out via gravity (that is, air's ability to float) overnight.

    If he did anything that resulted in air in the injector lines and he did not put in some pre-mix to cover it and then run it on the hose with the oil pump pulled open to bleed then he messed up.

    It does not take long to bleed the injector lines, btw.

    One thing to note on the '98 951. That year and that year only silver 951 requires teh oil pump to be indexed AFTER the final idle screw adjustment. If this was not done and the pump was bad enough out of index it could have caused a lack of lube (that or a combo of things).

    Still, wait until you see what the cylinder looks like. That will tell you. They do not need a lot of oil, even when running at high RPM. If the injector lines are not empty right now as it sits then they were not empty when it died.

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