GTX won't rev past 5k when warm

[Brando]

Bought a 1997 Seadoo GTX last summer. Seller says runs pre-mix.

Ran it half the summer. Jumped on it cold one day and it fell on it's face about 4k or so. Checked compression, 145-150.
Ran it the rest of the summer, sometimes good, sometimes wouldn't go past 4k, usually would go further if you let off the throttle and back on.
Tried unplugging red wire on rectifier, no change.
This winter, did the following:
- replaced all fuel lines
- pulled carbs, checked pop off valves for 30 sec hold. Could not check pressure, as they did not pop by 03 psi on gauge.
- cleaned carb prefilters, one was pretty dirty.
- rebuilt carbs and fuel pump, with all new gaskets, but did not disassemble pop off valve, or pull main jets.
- cleaned Rave valves, one was missing about a 3/4" chunk from the corner, replaced. Both had heavy carbon buildup (~1/16")
- replacement rave caps were set flush (as they came) old ones were down 3/16 or so.
- endoscoped from Rave valve hole and spark plug hole. rings still look intact, heavy carbon on top of piston.

Put it in the water, and it starts right up, runs great 1 or 2 pulls, then will not go above 4 or 5k. Rough idle after the 1-2 runs. Seems to smoke more than it used to or should.

Wondering if it's still running oil injection plus premix, or running too rich. It ran best when the oil tank was almost empty, used probably 1/2 tank last summer.
Seems extreme for just lubing the rotary valve, even if the seals are leaky.

Checked compression again, 145-150 rear, 150-152 front.

Any ideas? This was a father-son project, I'd really like to get a win.

Don't notice any water in the hull or exhaust, but will check that and see if the oil pump was truly disabled next. I know there was no cable going to the carb, but never looked down in there. The oil line with filter is still there, so I need to trace it down.

Thanks in advance

 

[mikidymac]

There is no point in messing with the carbs if you don't do it correctly and replace parts with Genuine Mikuni. Do the carbs and do it correctly or you are just going to keep chasing your tail.
Sounds like your oil injection system is still working and without the cable the oil pump goes wide open so you are running a ton of oil.

Also did you replace the fuel selector? Replace gray tempo fuel lines?

 

[Brando]

I'm hoping you are correct on the oil pump.
For test only, can I disconnect and plug the oil pump feed line, leave the two lines hooked to the rotary valve, and take a run?
Or can you turn it all the way down with the linkage?

If that works, do I need a blockoff plate? or just pull the drive gear, plug the lines, and put the pump back on?
leaving the rotary valve lines, of course.

Really wish I had thought of this when the carbs were off. Always verify what you are told...

all fuel lines were replaced and looked like original tempo,
carb kits were mikuni, I primarily opened the carbs to change the filters. I do not have the experience to go further, so I did not. They look clean, but I do wish I had the knowledge to check the main jet.
Fuel selector has not been replaced. I could bypass it for now to see if that makes it better.

Thanks for the help.

 

[JeremyD615]

Read through the carb rebuild sticky at the top of the forum. If you got them off and opened them up to clean them, you can do the rest of the work to rebuild them. It’s really a simple job once you’ve been in them and seen how everything works... That’s most likely where your problem lies.

As for the oil injection, there’s really no good reason to go premix on these things. The pumps are super reliable, and the only real maintenance is replacing the small oil lines on occasion and keeping the system full of the correct API-TC oil. I’d pull the pump off to make sure you’ve still got the driveshaft in place, and get a linkage cable ordered for it to go back to the factory setup.

 

[Brando]

Thanks for the responses.

Checked the oil pump and all the PO did was disconnect the cable. I pulled it and the driveshaft came out with it . Was worried about pulling the mag cover if I couldn't get it.

Capped the hoses, except those feeding the rotary valve and reinstalled the pump without the driveshaft.
Took the ski back out (61 degrees and 20-30 mph winds).
Idled better, smoke back to normal, but still 4k max rpms.

Put in a new set of spark plugs (gapped properly this time) and it ran great. (approx 6700 rpm, but I don't think he had room to straighten the steering and let it loose)

Thanks for all the help.

I'll let it run for awhile like this, then decide whether to reinstall the pump. If this was a fresh rebuild, I'd probably be more inclined. My 550sx is premix, so this keeps them the same. Plus, I blew a Yamaha GP 800 motor years ago when the oil line shrunk over time and pulled off. Why they had it pulled that tight with no hose clamp is beyond me.

 

[AKnarrowback]

How aggressive are you riding the machine? Are you doing "mellow" throttle changes or are you going no to full throttle in a second and varying the throttle quickly when riding?

Not wanting to throw another possible headache in, but I included a service bulletin for the 97 GTX that address a situation that blocks rhe motor from reving past 5000ish rpm's.

All the advice given to this point is spot on from people that know their stuff and I would follow their knowledge in trouble shooting and correcting things on your machine.

The reason I asked about throttle changes is because on my 97 GTX I could do a "drag race" start and rev up to top rpm's and speed without a problem. If I was riding aggressive with sudden throttle changes things ran good 90% of the time. If I was ever out for a cruise with long slow throttle changes I had an almost 100% chance of locking the motor under 5000, I could continue to open the throttle but no rpm increase, until I let off to no throttle and nailed it again where it would push past 5000 and run good. A note on this is that the 5k hesitation only happened after the motor was at operating temp, it wouldn't do it cold. The condition still existed when the rave valves were clean as well.

You said this is a Father Son project and you want a "win". From what you are describing you are very close and with the knowledge base on this site you will get it.

Keep us updated.

 

[Ckrawiec]

Bought a 1997 Seadoo GTX last summer. Seller says runs pre-mix.

Ran it half the summer. Jumped on it cold one day and it fell on it's face about 4k or so. Checked compression, 145-150.
Ran it the rest of the summer, sometimes good, sometimes wouldn't go past 4k, usually would go further if you let off the throttle and back on.
Tried unplugging red wire on rectifier, no change.
This winter, did the following:
- replaced all fuel lines
- pulled carbs, checked pop off valves for 30 sec hold. Could not check pressure, as they did not pop by 03 psi on gauge.
- cleaned carb prefilters, one was pretty dirty.
- rebuilt carbs and fuel pump, with all new gaskets, but did not disassemble pop off valve, or pull main jets.
- cleaned Rave valves, one was missing about a 3/4" chunk from the corner, replaced. Both had heavy carbon buildup (~1/16") - >>I WONDER WHERE that missing 3/4" chunk of metal went???
- replacement rave caps were set flush (as they came) old ones were down 3/16 or so.
- endoscoped from Rave valve hole and spark plug hole. rings still look intact, heavy carbon on top of piston.

Put it in the water, and it starts right up, runs great 1 or 2 pulls, then will not go above 4 or 5k. Rough idle after the 1-2 runs. Seems to smoke more than it used to or should.

Wondering if it's still running oil injection plus premix, or running too rich. It ran best when the oil tank was almost empty, used probably 1/2 tank last summer.
Seems extreme for just lubing the rotary valve, even if the seals are leaky.

Checked compression again, 145-150 rear, 150-152 front.

Any ideas? This was a father-son project, I'd really like to get a win.

Don't notice any water in the hull or exhaust, but will check that and see if the oil pump was truly disabled next. I know there was no cable going to the carb, but never looked down in there. The oil line with filter is still there, so I need to trace it down.

Thanks in advance

 

[Brando]

Hoping it went out the exhaust, or broke off during a prior cleaning. Carbon buildup indicates it was pretty old.

 

[Brando]

Thanks AKnarrowback, he's 14, so I doubt much light throttle. He is very cautious and aware, however. 'head on a swivel'

 

[Brando]

Any tips on setting the rave valves? Originals were about 3/16"below flush, used set was flush top of red cap to black

 

[mikidymac]

Either is fine. You can set them wherever you want as long as both are even.