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I know it's not a seadoo, but....

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lcichon

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Hey guys, I have a Seadoo XP but I also have a 1998 Kawasaki 900STX that's giving me issues. I was wondering if you could suggest some things to check as I can't seem to figure out what's going on with this ski.

Here's what it's doing:
After a few minutes of running just fine it starts losing power at WOT and you constantly have to feather the throttle to keep going fast. It starts and idles perfectly, and runs fine at lower rpms, and by feathering the throttle I can reach 40 mph, but if you just hit the throttle full blast sometimes it will bog and even after it gets going it will only the keep rpms up for a few seconds before losing power and eventually stalling if you don't feather it. Sometimes when you hit the throttle you can tell you're not at full power and you have to pump it a couple times to get full power which only lasts a few seconds before you have to repeat. Here's the kicker: sometimes it will run perfectly for an hour, 10 minutes, or 30 minutes before the problem comes back, which is why I thought I had resolved the issue several times just for it to return.

Here's what I've checked so far:
1. Removed the carb assembly and blasted carb cleaner in anywhere I could, checked butterfly valve operation/throttle cable adjustment.
2. replaced the fuel filter
3. verified the fuel tank is not on a vacuum by checking the vent line and opening the gas cap and closing it and experiencing the same issue immediately (thanks Seadoosnipe, I really though that was the issue until last night).
4. ran a few bottles of heat and carb jet cleaner through several gas tanks

What else can I check?

Thanks guys,

Lee
 
Do not use sea foam on a two stroke its a detergent and will eat away your internal seals. As for your problem what are the compression readings and have you done a carb rebuild yet?
 
Are you sure? I used it on my 96 GTX and it's fine. It cleared the whole thing up and it works perfectly.
 
YES im sure 2 strokes are not made to have a detergent ran through them. If you have only done it once you should be ok but dont do it again. As for lcichon get compression readings and report back with them if they are good then you need a carb rebuild possibly
 
YES im sure 2 strokes are not made to have a detergent ran through them. If you have only done it once you should be ok but dont do it again. As for lcichon get compression readings and report back with them if they are good then you need a carb rebuild possibly

Ok thanks man. I won't use it again. :agree: :thumbsup:
 
Sorry lcichon for usless help. It worked for me but I wouldn't try it if Brock says it could damage your jet ski. Maybe I got lucky and nothing bad happened... I dunno.
 
Sorry lcichon for usless help. It worked for me but I wouldn't try it if Brock says it could damage your jet ski. Maybe I got lucky and nothing bad happened... I dunno.

well.......... there is no useless information so dont feel bad alot of guys dont know this. Alot of guys run seafoam through their two stroke and wonder why they have to start replacing seals on it. This forum is to help each other and learn alot from it. After we get the compression readings we will go from there.
 
Compression test complete - 70 psi on all 3 cylinders. I'm headed out to Lake McConaughy this Wednesday for 4 nights of camping and will have the ski with me so this would be the perfect time for some lake testing. If you guys can suggest some things to check while the ski is in the water I'd be able to bring the right tools and give them a shot. Thanks!
 
Compression test complete - 70 psi on all 3 cylinders. I'm headed out to Lake McConaughy this Wednesday for 4 nights of camping and will have the ski with me so this would be the perfect time for some lake testing. If you guys can suggest some things to check while the ski is in the water I'd be able to bring the right tools and give them a shot. Thanks!

you need a rebuild with 70 psi. Sorry its time for a top end dont run it anymore or you will do even more damage pull off the heads and see what the cylinders look like you may be a ble to get away with just rings at this point if you DONT USE IT ANYMORE the factory compression is 135-150........ 70psi is terrible
 
This ski has less than 200 hours on it total. It sat unused for 10 years. I have a hard time believing it needs a new top end. I did but the compression test kit at harbor freight. Is it possible the tester is crap? And if 70 psi is only half how likely would it be that all three would be 70?
 
Do not use sea foam on a two stroke its a detergent and will eat away your internal seals. As for your problem what are the compression readings and have you done a carb rebuild yet?

I would say if you had an issue with seals and sea foam that the seals were bad to begin with. I've used it in every rotax engine I've ever had with no seal failure ever(6 ski and over 40 sleds since 1968). I also use it in my diesels with 2000+ psi pressures in the injection pump with no failures, two of them are over 350,000 miles and have never been touched. I hate it when good products get a bad rap because there was an under lying issue or it was used improperly. Funny how the boys at skidoo.com swear by it and the seadoo guys bad mouth it when they both use rotax motors.:rolleyes:
 
You can try another compression tester. but since it sat for 10 yrs and even if you got it running maybe some rust broke loose or maybe all the rings are stuck. Try another test then if still low pull the head off and look at the pistons and walls.

Report back to Brock by a post. Maybe some other people will comment too.
 
You can try another compression tester. but since it sat for 10 yrs and even if you got it running maybe some rust broke loose or maybe all the rings are stuck. Try another test then if still low pull the head off and look at the pistons and walls.

Report back to Brock by a post. Maybe some other people will comment too.

:agree: check with another guage and report back if numbers are the same or any lower than 130 you neeed a top end
 
Don't quote me on this... and I will have to check... but I think that engine only put out 125 PSI on a rebuild.

Regardless... 70 psi is going to be low on any high HP 2-stroke.

I have a couple of the HF compression gauges, and they are both spot-on with my expensive Snap-On gauge. You could have a bad one... but before taking it back... make sure there aren't any leaks in the hose... and test the gauge with an air compressor. (With a known good gauge)
 
Yep... a good top end will be 115 to 125 psi on that engine.

Seadoo runs much higher compression from the factory than most other companies (That's where Brok is getting 150 psi) but... that's why we have to run good oil... and Kawi allows the use of TC-w3. (less HP/liter)
 
Yep... a good top end will be 115 to 125 psi on that engine.

Seadoo runs much higher compression from the factory than most other companies (That's where Brok is getting 150 psi) but... that's why we have to run good oil... and Kawi allows the use of TC-w3. (less HP/liter)

ok cool thanks DOC learned something new today but regardlesss 70psi is definetly a rebuild and thats where your problems are coming from
 
Great info

Thanks for all of the great info! I will test the gauge for leaks and run a compression test on my Seadoo which just had a top end job to test it.
 
ok cool thanks DOC learned something new today but regardlesss 70psi is definetly a rebuild and thats where your problems are coming from

Yep... 70 is bad on any modern engine. (other than a lawn mower)

Thanks for all of the great info! I will test the gauge for leaks and run a compression test on my Seadoo which just had a top end job to test it.

97xp.... on a fresh top end SHOULD be 145 to 155 PSI.
 
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