97 GTX fine idle and power to 4500, then low power

[khriss]

Thank you in advance to any advice.
I am working on my neighbors GTX that cracked the cylinder buckets last winter. I got the jugs welded, and put the engine back together. Compression is good in both cly. Additionally, the ski had sunk due to the cracks in the engine, so there maybe water damage to anything that does not like water. (The engine mechanicals are fine)

So, now the problem: The ski runs fine at idle and up to 4500RPM. If more throttle is applied it will speed up for a second, maybe two, but then falls right back to 4500. It will again surge every few seconds but cannot maintain engine speed above 4500.

The plugs are functioning properly and look like any running 2 stroke.

I took all the TCW3 oil out and replaced it with API.

It will rev up on a trailer but it sounds lean (hollow) in the upper RPM range.

The fuel pump appears to be working in that it will fill the filter above the gas tank in about 15 seconds. I have not disassembled the carbs.

I am doing all of this as a favor, so I am trying to keep costs down to the owner, but I also do not want to keep dumping time into a common issue....if this is one.

Again, thanks to any that answer.
Khris

 

[johnson2_r]

have you checked the compresion on the cylinders ?

 

[khriss]

Sorry, forgot to put that in. Both cyl are 125psi, with the correct spark plug length adapter, but with a 10in hose, so they are probably closer to 140ish. So, yes, I think compression is fine.

I did just get off the phone with Dale's Jetsports and bought all new fuel line, a fuel selector valve and two carb kits (one for ea. carb). I am hopeful that the lines are clogging the carbs. It makes sense, in that the lines are original, and the accelerator pump is working, which causes the initial burst of power after 4500 RPM.

By the way, they said this is a common problem with skis this old running this new "wonderful" fuel.

Thanks for the question,
Khris

 

[kauffjd3]

http://seadooforum.com/showthread.php?t=18070

same thing?

 

[khriss]

Sounds like the exact same issues. I will work on the ski Monday or Tuesday, and report back.
Khris

 

[khriss]

Update

I spent 5 hours today rebuilding both BN38s replaced all the fuel line and the selector valve. While I have not run it in the water yet (maybe tonight?) it sounds like an entirely different beast now. The throttle snaps nicely and has a deep growl compared to before.
The front carb (no pump) had a hole in the diaphragm and the inlet filter was quite plugged with black rubber. The rear carb and fuel pump appeared operable but I rebuilt it anyway.

I think it is fixed!!!

Khris

 

[johnson2_r]

right on good to hear good luck right back let us no how everything went.

 

[khriss]

I used the wrong release springs causing a lean top end. I caught it quickly and did not damage anything. For some reason I thought the 115g spring went in with a 1.5 seat, but it should be an 80g. My pop off gauge confirmed the issue.....so all is right now with this SeaDoo that I feel very intimate with......now on to my 550SX that lost a cly this weekend
Khris