1997 GTX Bogging - can't figure it out

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cairnclub

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Hey guys, long time lurker and just joined. Awesome community.

Got a headscratcher

Just picked up a 1997 GTX 787 twin carb with new engine installed (has paperwork to back it up but does not specifically say what was replaced.

Bogging/won't rev up much past 3500 RPM, on land or in water no real change. 2 mph in water. Starts right up and idles nice (3000 rpm on land, 1500 in water)

150 psi in both cylinders, I have rebuilt the carbs with real mikuni kits (set carbs to seadoo specs, correct pop off pressure, all jets clean and clear) and replaced all fuel/oil lines and filters. I installed a new rectifier as well - ski is now making perfect voltage and no AC voltage (was kinda high before but did not affect issue)

I tried adjusting low speed needle in 1 turn and out 1 turn in increments of 1/4 turns to see no real changes

Also has new plugs, good gas and good oil.

Does this sound like RAVE valves?

Any ideas appreciated, hopefully pics work
 

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Don't mess with pop-off. Use the correct needle and seat and spring and as long as it is within spec it is fine. Don't mess with pop-off to fix a running issue as that is not the issue. A stock seadoo at normal altitude will run perfect with all stock carb settings.
 
mikidymac said:
Don't mess with pop-off. Use the correct needle and seat and spring and as long as it is within spec it is fine. Don't mess with pop-off to fix a running issue as that is not the issue. A stock seadoo at normal altitude will run perfect with all stock carb settings.
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Ok I will keep that in mind. Anything else to check before taking everything apart again?
 
You have covered the basics, carbs, compression, voltage.
Have you tied running a fuel line directly from the RES fitting on the fuel tank to the carbs? This would eliminate the fuel strainer and selector as possible issues.
 
mikidymac said:
You have covered the basics, carbs, compression, voltage.
Have you tied running a fuel line directly from the RES fitting on the fuel tank to the carbs? This would eliminate the fuel strainer and selector as possible issues.
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Forgot to mention I replaced both of those as well. Everything from the tank to the carbs is new
 
Like before check RV timing.did you replace the crankcase pulse line to fuel pump.for just incase did you try running with no fuel cap incase tank vent check valve stuck.is the cup filter oring pinched.
 
Poormanracing said:
Like before check RV timing.did you replace the crankcase pulse line to fuel pump.for just incase did you try running with no fuel cap incase tank vent check valve stuck.is the cup filter oring pinched.
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Also check and make sure the ground going from battery thru rear electrical box to the coils are tight they use a cheap ass bolt into plastic and looses ground and won't rev up.also run another ground from battery to the block can be a temp one for testing purpose
 
Poormanracing said:
Also check and make sure the ground going from battery thru rear electrical box to the coils are tight they use a cheap ass bolt into plastic and looses ground and won't rev up.also run another ground from battery to the block can be a temp one for testing purpose
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Thanks poor man, I replaced that ground and tested it 0 ohm. Checked several places on the block and heads all 0 ohm ground. I did replace the pulse hose. No change. Also ran without gas cap for about a minute. Also no change. I tested about 5.8k ohm on each spark plug wire. Just ordered a new coil and wire set.
 
Ok so I tested the stator and everything looked good (all yellows have no shorts to ground) also installed new coil and plug wires no change

BUT

I think I found something

I started probing around and found that on the plug going to the stator, 4 of the 6 terminals shorted to ground and 3 of them shorted together with 0 Ohms.

This is with battery installed and key off.

The circled yellow ones are shorted together
The circled red ones are shorted to ground

Is this normal? I thought all the yellow phase wires would not be grounded.

Bad CDI ?
 

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Sounds like you have a bad rectifier. They are cheap. Don't buy the $100 marvel as you don't need it. :) The Mag Plug on the engine should be giving you, on the yellow wires .3-.7 ohms. None should be grounded. Black wire is ground and I think the red is the positive.

A bad rectifer will make the ski run like crap. I had one take out my ECU on a 1996 SPI. Easy to replace. You can unplug the rectifer and run the ski but the battery won't charge.

That said, your 3500 RPM problem may be a different matter. If it presists make sure the rave valves are free and not binding. Check your compression. I often warn carb builders of the 3 small small holes in the carb throat. They need to be clear and flowing copious amounts of fuel. I fought 2 1996/1997 GTXs and until I got those holes clear. The skis had trouble transitioning to the high speed jets.

You have a 1997 GTX which has a technical service bulletin concerning the rave valves but that isn't your problem right now.

Good Luck !
 
Thanks templet !

I replaced the rectifier already and it made no change. Took the RAVE valves out yesterday and they are moving nice and smooth also no side to side movement.

Compression is 150 psi in both cylinder + - 2 psi with known good tester. I think 150 is healthy for the 787.

It won't even rev when I squirt a little gas down in the carb throats which is what makes me think it is a spark not fuel issue.


I ASSUME my new rectifier is good because it runs exactly the same as before I changed it and now its making perfect voltage at the battery while running (and as high as it CAN rev) and 0 AC voltage

I think I'm gonna test the wiring between the stator and the rectifier?
 
You do have a head-scratcher there. :) I have not ever checked the AC Voltage at the rectifier. I've always checked it at the battery. I don't understand how you can gave "0" AC voltage and the correct voltage at the battery.

I once started a 787 with the rave caps off and it did just what your ski is doing. :) If they open too soon that is a problem but they shouldn't if everything is in place. :)

You can check your rubber exhaust hose in the back. Those can cause a restriction if they come apart on the inside. It blows up like a balloon internally.

You could also have some crap inside the mag housing, rust and corrosion that prevent the ignition trigger from detecting the timing point as it should.

Worse case is the ski jumped time because the brass gear on the crankshaft is bad. Let's hope that isn't a problem. Good Luck !!
 
Oh sorry I did not make that clear - I was testing for AC voltage at the battery while running - that is 0 or very close to it.

Now that I have to ski off the lift and into the garage I'll be tearing into it more.

I will check the rubber exhaust hose - it does seem kinda weird and floppy..

I am thinking of pulling the mag cover as well just to check things out.

OH also it now backfires when starting - but not at all while running

The mystery continues...

Thanks all
 
:D If I rev it and the voltage doesn't change at the battery... I swap it out. They way batteries are today, most being pure junk, you gotta make sure the battery is good so you don't get a false reading. Good Luck !!
 
etemplet said:
:D If I rev it and the voltage doesn't change at the battery... I swap it out. They way batteries are today, most being pure junk, you gotta make sure the battery is good so you don't get a false reading. Good Luck !!
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etemplet - I think you may have solved this

check out my exhaust hose

I'll be ordering a new one and update the thread with results

THANK YOU
 

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cairnclub said:
etemplet - I think you may have solved this

check out my exhaust hose

I'll be ordering a new one and update the thread with results

THANK YOU
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Dude, I wish I was that lucky fixing my own shiznit !! LOL Post up and let us know how you make out !! Good Stuff !!
 
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