1998 GTX LTD Hard start/poor performance

[Geto137]

Hello all,

So I’m new the forum and recently have been going mad with this ski.

PROBLEM:
It is very hard (if will at all) to start in the water, doesn’t want to idle well and won’t run over 5-6k RPM with a top speed at about 47mph. On the trailer if you get it running it will hit the limiter. It used to run great. If I hit a wave and come down it bogs down a little.

INFO/WHAT IVE TRIED:
-Replaced oil pump cable (found it snapped earlier this year)
-Cleaned carb, blew out all the passageways.
-Inline fuel filter right before carb
-13-14V on the battery at 4000rpm
-replaced the rave bellows (one was leaking oil at the O ring)
-pulled a plug wire at a time while running, both cylinders have spark at an idle on the trailer
-replaced jet pump with used part, worked fine at one time on this ski this year
-rerouted fuel line from the “on” port of the fuel selector direct to the front fuel filter


If anyone has some suggestions I would really appreciate it, this thing has hauled ass earlier this year and I just can’t seem to shake the gremlin....

 

[glsmohio]

What's the compression?

 

[Geto137]

What's the compression?

I’m going to do another compression test today, last time I remember it being close about 140-150 not sure what is desired.

 

[JeremyD615]

First, get rid of that inline filter. They cause more problems than they solve, and the factory filter works very well... I’ve seen them cause fuel flow problems as well as air leaks, so let’s eliminate that variable.

Next, rebuild the carbs using GENUINE Mikuni parts and new needles and seats. Follow the carb rebuild sticky... 90% of these types of problems are fuel related. Start there, and come back if it’s still acting up and we can dig in further...

 

[Geto137]

First, get rid of that inline filter. They cause more problems than they solve, and the factory filter works very well... I’ve seen them cause fuel flow problems as well as air leaks, so let’s eliminate that variable.

Next, rebuild the carbs using GENUINE Mikuni parts and new needles and seats. Follow the carb rebuild sticky... 90% of these types of problems are fuel related. Start there, and come back if it’s still acting up and we can dig in further...

After rereading the thread I’d like to believe I followed it pretty closely. I removed the inline filter and still no dice. Also occasionally the idle on the trailer will only be about 1800RPM.

 

[Ckrawiec]

After rereading the thread I’d like to believe I followed it pretty closely. I removed the inline filter and still no dice. Also occasionally the idle on the trailer will only be about 1800RPM.

Trailer IDLE (in air) should be 3000rpm, Idle (in water) will drop to 1500. Your trailer IDLE is low....I'd say your need some carb adjustments on the screws to fine tune them ....BUT, the ski really needs to be in water to dial it in properly...sitting on a trailer in enough water is fine....

 

[JeremyD615]

Did you replace parts, or just clean them? I’m still thinking this is a carb issue...

 

[Geto137]

Did you replace parts, or just clean them? I’m still thinking this is a carb issue...

I replaced parts AND cleaned with solvent and compressed air. Also, the idle will get up to 3000 if you blip the throttle a few times and stay for a minute and go down over time.

Am I maybe having a baffle or tank vent issue? Should I try reserve instead of “on”?

 

[mikidymac]

Did you use only genuine Mikuni carb parts?

Something is wrong with your carbs if the idle hangs high then drops.

 

[Geto137]

Did you use only genuine Mikuni carb parts?

Something is wrong with your carbs if the idle hangs high then drops.

Yes. On the trailer it can sometimes only rev up to let’s say 6000rpm, then after a few seconds of WOT it’ll get up to the limiter and then run at 3k idle.

 

[mikidymac]

Running on the trailer is worthless for diagnosis, you have to have it in the water with a load.

 

[Ckrawiec]

Yes. On the trailer it can sometimes only rev up to let’s say 6000rpm, then after a few seconds of WOT it’ll get up to the limiter and then run at 3k idle.

What mikidymac is succinctly saying is...the WATER IS THE LOAD. The ski really needs to be wet to really test whats going on.....sitting on a trailer IN ENOUGH WATER will work (yes it a PITA to be in the water) but that's the tried and true method to dial these skis in.....they ALWAYS seem to run great on the trailer.....makes you want to pull your hair out, can be very frustrating...you think you got it dialed in, then whamo....falls flat on her face on the first test run......the ski will keep you humble!

 

[Geto137]

I really can’t work on it at the ramp sadly. Just seems like I’m out of options and can’t seem to find the culprit of it not wanting to start and run wel under load...

 

[Geto137]

I purchased ANOTHER genuine rebuild kit, will be in this week. Anything else I can check OTHER than the carb that I haven’t in the meantime?

 

[Ckrawiec]

Desparate times equal desparate measures....ever consider building a pool around the ski ..... 2’ deep wooden structure with a plastic liner filled with water....restrain the ski and have at it.

 

[Geto137]

Desparate times equal desparate measures....ever consider building a pool around the ski ..... 2’ deep wooden structure with a plastic liner filled with water....restrain the ski and have at it.

I’ll refer to the carpenters sticky after I try all the other ideas haha

 

[Geto137]

UPDATE: After another sea trial, still won’t go above 6k (carb hasn’t been rebuilt for the second time yet). It didn’t want to start at home on the house, but after leaving it to sit for a day or so, boom fires right up, but still runs meh. I guess we will see what happens after ANOTHER carb rebuild

Compression on both cyl is about 115

Both plugs had black crust on them

 

[JeremyD615]

When you say you had a hard time starting it on the hose, how are you doing that? These skis need to be started and running before the water is turned on. If the water comes on before the motor is started, it will flood the exhaust and then the motor with water...

The only time I run mine on the hose is to back flush the cooling system. The carbon seal will overheat long before the motor does, and it is not cooled when running on the hose. My suggestion would be to fire it up in the driveway to be sure it will start, and then take it to the water for any further testing...

 

[JeremyD615]

Compression on both cyl is about 115

Both plugs had black crust on them

You also need to double check that compression gauge. At 115psi, if that number is accurate, the top end of that motor is done... Unfortunately that would explain the hard start, the fouled plugs, and the poor performance as well. Check it with another gauge, but I have a feeling you’re going to be rebuilding the top end of this motor...

 

[Geto137]

You also need to double check that compression gauge. At 115psi, if that number is accurate, the top end of that motor is done... Unfortunately that would explain the hard start, the fouled plugs, and the poor performance as well. Check it with another gauge, but I have a feeling you’re going to be rebuilding the top end of this motor...

The gauge has about 8in of hose on it to reach into the bilge. I would also think this isn’t the case considering The numbers are so close and consistent. If one was 135 and the other 95 I’d be more quick to jump into the top end....

 

[Ckrawiec]

The gauge has about 8in of hose on it to reach into the bilge. I would also think this isn’t the case considering The numbers are so close and consistent. If one was 135 and the other 95 I’d be more quick to jump into the top end....

I think you missed the point.....what Jeremy is saying is double check those compression numbers with a better guage.....compression should be 150 psi (or near that number in both cylinders). Your 115 is low and could indicate a top end rebuild...but it always pays to double check the compression readings a couple times (ideally with a couple guages to backcheck and cross reference) just to hopefully rule out a bad guage reading and extra un-necessary work.

 

[Geto137]

I think you missed the point.....what Jeremy is saying is double check those compression numbers with a better guage.....compression should be 150 psi (or near that number in both cylinders). Your 115 is low and could indicate a top end rebuild...but it always pays to double check the compression readings a couple times (ideally with a couple guages to backcheck and cross reference) just to hopefully rule out a bad guage reading and extra un-necessary work.

Will do. Also the motor wasn’t hot nor wet for this test. Why have I read that the 951 should be anywhere from 100-135PSI vs 150? I was told the smaller motors should be about 150 but the 952 needs to be below 135 with wear to avoid detonation.

 

[mikidymac]

The Carbed 951 should be 130 psi for a perfect engine, at 110 they are done and typically will not start in the water.

To test compression ski should be cold, out of the water, plug wires grounded, fuel off and throttle held wide open.

 

[Ckrawiec]

Will do. Also the motor wasn’t hot nor wet for this test. Why have I read that the 951 should be anywhere from 100-135PSI vs 150? I was told the smaller motors should be about 150 but the 952 needs to be below 135 with wear to avoid detonation.

Oppps, my apologies....I was thinking a smaller engine for the compression number.....Mikidymac answered -> 130 psi.

 

[Ckrawiec]

Hello all,

So I’m new the forum and recently have been going mad with this ski.

PROBLEM:
It is very hard (if will at all) to start in the water, doesn’t want to idle well and won’t run over 5-6k RPM with a top speed at about 47mph. On the trailer if you get it running it will hit the limiter. It used to run great. If I hit a wave and come down it bogs down a little.

INFO/WHAT IVE TRIED:
-Replaced oil pump cable (found it snapped earlier this year)
-Cleaned carb, blew out all the passageways.
-Inline fuel filter right before carb
-13-14V on the battery at 4000rpm
-replaced the rave bellows (one was leaking oil at the O ring)
-pulled a plug wire at a time while running, both cylinders have spark at an idle on the trailer
-replaced jet pump with used part, worked fine at one time on this ski this year

FROM YOUR ORIGINAL POST>>>>>


-rerouted fuel line from the “on” port of the fuel selector direct to the front fuel filter <<<What does this mean???? When you say " the front fuel filter"...do you mean the fuel/water separator???