1998 GTX LIMITED high rpm bogging/breaking up

[Lamp_Post]

I’ve been struggling with this issue on my GTX since I’ve got it.

Things I’ve done and checked

Rebuilt carb is OEM OSD parts.
New fuel horses.
Checked and verified pop off.
Checked for leaks in entire fuel system.
Verified no leaking in RAVE valves and they do open.
Verified rectifier is outputting about 13.7 V at 4000 rpm.
Probably some other things I’m forgetting.

Here’s a video to show the issues I’m having -

The issue - The ski will idle great and low rpm react fine. But under 3/4 to full throttle it will sound like it’s bouncing off a lower rev limiter. After like ~ 10 minutes of driving it will get worse where I can only idle if I try to give it gas it will die or if I go slow enough onto gas it will pick up some. I can actually hear it’s running on 1 cylinder then the second will come in and out sometimes. (Sounds like it is running on 2 cylinder’s for the first 10 mins and maybe idle?)

I’ve rebuilt the carbs twice and can’t see how it would be a carb issue at this point…

 

[etemplet]

First off did you check engine compression? Did you replace the spark plugs?

Sounds like fuel to me. I've seen some weird stuff with these skis. Describing things to check is difficult without hands on the ski. Did you replace the check valves on the fuel pump in the carb? They are easy to damage.

How did you check the fuel system for leaks??
Testing for leaks, I clamp the ON and RET hoses right at the fuel baffle and I pull a vacuum on the carb feed line. I switch the fuel selector. Then I pressure the system to 10psi and get out the soap bubbles. I remove the clamp on the RET and ON lines one at a time and I pressure up and check for leakage on the fuel selector. A common leak point is the water separator. By chance did you intall an in-line fuel filter? If so remove it.

How did your reed valves look? Sealing properly? (I'd check this later on not at the beginning)

Here is a weird one. If your fuel gauge is reading.... what is the fuel level reading when your engine starts acting up?? Yup I had a problem with the screen at the bottom of the fuel baffle and the engine would drain the fuel inside the baffle and kill. Even with a full tank enough fuel could not get into the baffle.
Did you loosen the fuel tank cap when your engine started acting up?
Did you try pulling the choke to see if the engine runs better or worse?

This is not a comprehensive list of weird shiznit either. LOL Just a few things to check

 

[Lamp_Post]

First off did you check engine compression? Did you replace the spark plugs?

Sounds like fuel to me. I've seen some weird stuff with these skis. Describing things to check is difficult without hands on the ski. Did you replace the check valves on the fuel pump in the carb? They are easy to damage.

How did you check the fuel system for leaks??
Testing for leaks, I clamp the ON and RET hoses right at the fuel baffle and I pull a vacuum on the carb feed line. I switch the fuel selector. Then I pressure the system to 10psi and get out the soap bubbles. I remove the clamp on the RET and ON lines one at a time and I pressure up and check for leakage on the fuel selector. A common leak point is the water separator. By chance did you intall an in-line fuel filter? If so remove it.

How did your reed valves look? Sealing properly? (I'd check this later on not at the beginning)

Here is a weird one. If your fuel gauge is reading.... what is the fuel level reading when your engine starts acting up?? Yup I had a problem with the screen at the bottom of the fuel baffle and the engine would drain the fuel inside the baffle and kill. Even with a full tank enough fuel could not get into the baffle.
Did you loosen the fuel tank cap when your engine started acting up?
Did you try pulling the choke to see if the engine runs better or worse?

This is not a comprehensive list of weird shiznit either. LOL Just a few things to check

About the only thing I haven’t checked yet is the reeds. Might just have to rip out the carbs for the 3rd time and recheck everything.

 

[TheGTIjetguy]

You can also try running without the seat on. Exhaust leaks can scavenge all the oxygen out of the hull and kill the engine.
Have you considered spark? I’d admit your video sounds like a fuel delivery issue but I had a bad coil that wouldn’t allow it to rev beyond half throttle. Idle and low power ran great.
Running with an inline spark tester could show that I suppose.