GSX 98 runs lean around 3/8 throttle

[Matslor]

Hello! i just bought my first sea doo. It's a gsx limited 1998.

i have problem running it around 3/8 throttle(3600rpm). It seems lean. i have searched the forum and found alot of help regarding this, but i find it strange that i can make the craft run perfectly by ''compensate'' with the choke.
Does anyone have the same problem? I am worried i will destroy the engine(?)

i pulled out the carbs and cleaned them and changed filter diaghram and sealing.
tried the low speed adjuster, but now i only reach around 4000rpm.
I have not tested the pop off or compression. previous owner changed the pistons last summer.
After running it for 15min the engine seems cold..? No problem to touch the cylinder or exhaust pipe.

Hope someone can help me. Sorry for the bad writing, but im from Norway.

 

[ryffish]

I had a gtx 96 and my gas valve wore out on me I had to turn valve to reserve so it would get more gas. If I didn't turn it to reserve it starved engine of gas . Also check linkage

 

[Matslor]

Thank you, this is helpful.
I have noticed that when the engine is cold, it's easier to start when the valve is turned to reserve. How was you're engine?
Did you change the valve?
Linkage is also checked, forgot to mention that.

 

[Coastiejoe]

The fuel selector valve is known to fail. When it does, it will either limit the fuel getting to the engine and or will allow air to be sucked in. In the later case, this leans out the mixture and can cause serious engine issues. At the very least, I would bypass the valve and see if things improve..

 

[ryffish]

I ended up changing the valve . By the way I had a 96 gsx it was a typo . But I loved the machine very pretty and fast . But don't rule out carburetor . Did you check compression?

 

[Matslor]

Thank you guys! I will check the valve and maybe bypass it.
Gonna check compression also.

 

[Matslor]

I ended up changing the valve . By the way I had a 96 gsx it was a typo . But I loved the machine very pretty and fast . But don't rule out carburetor . Did you check compression?

Compression is 135 on cylinder 1 and 140 psi on number 2

 

[ryffish]

That's not bad it's not causing your problem . Did you bypass the fuel valve ?

 

[ryffish]

No fuel leaking anywhere is there

 

[Mickirig1]

Sounds like your sucking air at 3/4 throttle. Been there, chased it for a month. Look at gasket in the front on water separator / fuel filter under hood. They go bad or bypass it and add an inline fuel filter before carb. Pop off tester can be used to pressure test the fuel system. Repair manual has the procedures. You can get the repair manual online too. If you do not have a pressure release when you open gas cap you have a leak somewhere.

 

[Matslor]

I pulled out the fuel selector valve and cleaned it. (First with diesel, and then with compressed air) It seemed fine when blowing at the same time as i tried the different selections. Dont think it was clogged but something came out. Should i change it anyway?

I cleaned the filters in the water seperator and inspected the gasket. Could not see anything wrong.

Could it be the rave valves that cause the problem?
After driving it for about 30 mins the engine is still ice cold. No heat when i touch the cylinder or exhaust pipe.

Gonna take it to the lake this weekend and check.

 

[Mickirig1]

Like I said, you need to pressure check your fuel system. With a pop off tester, if you have an air leak, you will find it. At high engine speeds and fuel demands it is easier to suck air then fuel. I chased the same problem for a month. I am very mechanically inclined. So I learn systems quickly and diagnosis problems. As far as the engine and exhaust being not hot. It is designed to have very good cooling,since it is enclosed in the hull. I can put my hand on any part of the engine or exhaust and hold it there. It's the design of the systems.

 

[Matslor]

thank you mickirig1. i will pressure check the system when i can get the tool needed.

A little update from last time :

Today i tried the jetski on the lake to see if it got any better. at the first 3-4 minutes it worked perfectly! but after that it was back to almost as before. its a little better. i dont need to compensate with the choke at high rpm's anymore.
Last night i cleaned the rave valves. they were very oily! i was driving around about 30 mins and the first thing i did after was to take a look at the rave valve again. look at the picture, is this normal?

 

[Mickirig1]

If you hit swells or wakes the gas will cover / wet the gasket on the fuel filter and make it seal. Then it runs right. DRYS OUT IT STARTS AGAIN. One of the reasons it drove me crazy!! Some years of ski's have oil tanks that do not hold pressure. A Defect of the two piece tank design. Junction of tank half's not completely sealed. Since it is part of the vent / air replacement system. This can effect the gas flow / negative pressure of the fuel system. Hense, Why you pressure test the fuel / vent system. the repair manual has the procedure. Download off the Internet if you do not have. Can't get a pressure tester? We can give you suggestions on replacements for it. Or places that have them cheap. OSD parts is one.

 

[mikidymac]

FYI: if you are running lean and you keep water testing it before actually finding your issue you will blow that engine up. They don't like running lean again and again.

 

[Matslor]

I mix oil in fueltank (previous owner disconnected the oil hose because of engine safety he said)
The hoses are sealed with bolts and zip ties.
If i understood you right, maybe this could affect fuel flow?

 

[Matslor]

Yes i am worried to ruin the engine, but the problem is in water. Runs fine without any hesitation out of water with gardenhose attached.

 

[Coastiejoe]

Yes i am worried to ruin the engine, but the problem is in water. Runs fine without any hesitation out of water with gardenhose attached.

Out of water running ONLY means that the basic components and engine are doing what they should.

Until it is in the water and has a load on it, you really can't determine to what degree it will run.

As a general, anytime you need to add choke, it is running lean. And a lean engine WILL destroy itself. It can eat a hole in the piston very quickly...

 

[mikidymac]

Good advise Coastie but this is a 98' Limited so no electric fuel pump or injectors.

 

[mikidymac]

I think we need to get back to the basics with this one as you have a few issues.
1. If it got better with the choke it is running lean.
2. You said after 30 minutes of riding the engine is ice cold. That is not normal, it should be warm or almost hot to the touch.

 

[Matslor]

1. Yes, runs great when applying choke at 3600-4000 rpm / 3/8 throttle.

2. Cant feel any heat when i touch the cylinder.

 

[Coastiejoe]

Good advise Coastie but this is a 98' Limited so no electric fuel pump or injectors.

I was just making a point... Didn't mean to imply anything more than that...

My point was/is,, If you do not KNOW you have good basics, nothing else matters...

 

[Chester]

You said you went through the carbs, does the accelerator pump operate properly?

Chester

 

[Mickirig1]

By using the pressure tester to check your fuel system you may find air leaks. There is also vent and intake pieces in the fuel lines that need replaced after so many years. Until you test the fuel line and vent system using the guide of the repair manual. You can not be sure of the problem. Once these parts are cleared. Then we can figure out if the carb or carbs are the problem. hopefully you have made sure all your electrical connections are good. Clean and protect with dielectric tune up grease. Auto part stores in your area may sell the big tubes of it.

 

[Matslor]

I was pretty sure the problem was the accelerator pump because only one carb got fuel from the pump when testing it. After cleaning it and applying compressed air through the fuel hose it opened and both carbs got the same amount of fuel when accelerator pump was activated.
So after this the pump operate properly.