97 GTX Problem has me stumped

[97_Sea_Doo_GTX]

Hello everyone,

Hoping to get some advice on an issue I'm having with my GTX. Took it out last week and it started out running great. After running it a couple of miles it acted like it was starving for fuel and finally died and wouldn't restart. Had to be towed back to the ramp.

First thing I did was check the plugs. They were light gray so it confirmed it was running very lean. Next I checked the compression. 145 on both cylinders. Checked the water separator/filter and it was clean. Disconnected the fuel line at the carb and was able to easily suck gas through with the shutoff (replaced late last year) turned to ON and then RESERVE. Fuel flow stopped as it should when I turned the valve to OFF.

Took the carbs off and took them both apart. I rebuilt them a few months ago with genuine Mikuni kits, needle valves & seats. Everyything was spotless and the screens were completely clean. Checked pop off pressure and it is about 36-37 on each carb. Put the carbs back together and reinstalled them.

Removed the baffle from the fuel tank and there were no problems with it at all. The screen was very clean and both pickup and vent tubes were clean. Blew compressed air through all fuel lines and they were free. They were changed to 1/4" rubber fuel hose right before I got the machine.

I then removed both fuel tank check valves and confirmed they were working as they should. The pressure release check valve only opens with a little pressure applied and the vacuum check valve flows freely toward the tank. I also looked inside the tank through the baffle hole and it looks spotless.

After putting everything together, it fired right up and sounded great on the trailer. This morning I took it out to the lake and it ran pretty good at first. had a little bit of a bog but snapped out of it and ran up to 6500 rpms. It used to run up to 6700 rpms. As I drove it more the top rpms kept on creeping down just like last week until it would only idle and, even then, not very well. Turned the shutoff to reserve which made no difference and I removed the fuel cap which also made no difference. Barely made it back to the ramp.

The new spark plugs are light gray again. Battery voltage was at almost 13 volts when I got back home so it seems like the battery is keeping the voltage up to normal.

Where do I look next? I can't put my finger on what is causing the lean condition after running for a period of time and then acting like it's completely starved for fuel. Any advice will be greatly appreciated. This machine had been running very strong until last week and it seems that I've checked all of the logical areas, at least all that I can think of.

Sorry for the long winded post but I wanted to make sure I covered everything I've done to try and resolve this issue.

 

[Lothsahn]

That's pretty thorough diagnosis. I don't have an answer, but did you check the pulse line from the engine to the mag carb? Is it snug? If it is loose, maybe it's leaking as the engine heats up? The pulse line runs the fuel pump.

You might also consider bypassing the fuel selector just to rule it out as the cause, although I realize that you did troubleshoot it.

Did you consider pulling choke when it's running lean to see if that made it run better?

Another option is that if the engine is somehow sucking air downstream of the carb, it could make it run lean. For instance, if a gasket leaks only when the engine is hot.

 

[97_Sea_Doo_GTX]

That's pretty thorough diagnosis. I don't have an answer, but did you check the pulse line from the engine to the mag carb? Is it snug? If it is loose, maybe it's leaking as the engine heats up? The pulse line runs the fuel pump.

You might also consider bypassing the fuel selector just to rule it out as the cause, although I realize that you did troubleshoot it.

Did you consider pulling choke when it's running lean to see if that made it run better?

Another option is that if the engine is somehow sucking air downstream of the carb, it could make it run lean. For instance, if a gasket leaks only when the engine is hot.

Thank you for the reply. I did check the pulse line and both clamps are tight but maybe it is cracked. I'll check that out.

I actually did try the choke when it was acting up and it didn't help. Just wanted to kill the motor.

I'll bypass the fuel selector just to rule it out. You never know if a seal is dislodged and creating an intermittent lack of fuel.

As for an air leak, that's a possibility but I'm not sure where it might be leaking. The carb to manifold gaskets are new but I might replace them just to rule that out. All of gaskets and seals in the carbs are new and I just took them apart and reassembled them.

I've been around and worked on engines my whole life. This one has me baffled. I really appreciate the input!

 

[POPPS]

Gray plugs often means top end damage.

 

[97_Sea_Doo_GTX]

Gray plugs often means top end damage.

I don't think the pistons are damaged yet. It didn't run very long with the lean condition. I looked in the cylinders through the plug holes with a scope and and the domes and cylinder walls looked ok. Compression is the same as it was before this all started. i just don't want to run it too much longer with the lean condition. Hoping that bypassing the selector will solve the problem.

The pulse hose turned out to be in good shape and was clamped snugly.I changed out the carb base gaskets with new ones. I'm temporarily bypassing the water separator just to take it out of the equation as well. Hoping to take it to the lake tomorrow and running it on the trailer for while to see what happens.

 

[etemplet]

If you pulled the choke out and it ran worse you are not lean. You have other issues. Did you replace the spark plugs? As mentioned concerning your compression is suspect unless you checked it with a good gauge. Low compression will cause incomplete burning of fuel and will fould the spark plugs When it runs bad, replace the spark plugs only and nothing else. Or, you could just check the compression on both cylinders. Sounds like you are doing some thorough troubleshooting. Sometimes these skis re really sneaky. We've all be down the rabbit hole. LOL Good Luck. Post up your findings.... curious minds and all that.

 

[GGuillot]

As mentioned concerning your compression is suspect unless you checked it with a good gauge.

He did ck compression, he said in the first post he's got 145 on both cylinders. I'm not sure if pulling the choke is ever gonna make it run better, that doesn't seem like a method I'd trust to tell me anything. The fuel selector bypass is the step in the right direction.

 

[97_Sea_Doo_GTX]

Just got back from the lake and it's not running any better. I put in new plugs yesterday before I ran it or made any changes and new plugs again today after I bypassed the fuel selector and water separator.

I had a difficult time starting it in the water today. Pulled it out of the water and finally got it running. Put it back in the water and it started but ran rough at first. Once it cleared up, it revved up fine so I went for a ride. Got on plane quickly with no hesitation or bog at all but would only run up to 5000 rpms and surge & misfire. Backed off the throttle and it would smooth out. Idled back to the ramp through the no wake zone and the idle rpms kept dropping until it wanted to die. Feathered the throttle and they'd come back up to the original 1500 rpms then drop again.

Got home and removed the plugs. Took a picture. Let me know what you think. The one on the left is the PTO plug and the one on the right is the Mag plug. Not as light colored as they were before but they still don't look right and aren't equal to one another. This was after about 10 minutes of run time. Compression is still the same.



I'm not sure what I've got going on here. I will probably get another compression tester and compare to what mine reads but the compression looks to be the same as any other time I've checked it. I might pull the head just to check the pistons and cylinders. Maybe there's an electrical issue?

Please let me know your thoughts. I really appreciate it!

 

[etemplet]

Pull the head. as Popp's said... shouldn't be gray. That's aluminum on the tips of those plugs.

 

[97_Sea_Doo_GTX]

That's what I thought about the plugs. But I still need to find out what is causing this issue. Something is making it run lean. No use replacing pistons and cylinders until l know what the root cause is first.

 

[97_Sea_Doo_GTX]

Pulled the head and the piston & cylinders look good. No scratches or gouges in the cylinder walls that I can feel with my fingernail. However, most of the carbon is cleaned from the piston domes telling me this thing is still running lean.

I'll keep on investigating. Not sure where to go from here.

 

[GGuillot]

I'd get the carbs back off, you were running fine before and now this problem. I'd be guessing to say with grey plugs and the clean piston tops it's ingesting water or something. Water and oil make a light grey....and the cylinders look great for an engine running lean..

 

[97_Sea_Doo_GTX]

You know, now that you mentioned water and oil mixing, maybe the head was leaking a little water into the cylinders. That might explain a lot of how this thing has been acting. I'll check the head and cover for cracks or any other signs that water might be entering the cylinders.

If that's all good,, I agree that something could be up with the carbs but gray color on the plugs looks a little strange for a simple lean condition.

Thanks for adding your thoughts on this! More than likely it's something I'm just overlooking. Good to have you folks giving me ideas and advice!

 

[emspjay]

I think it might be something in the carbs. I never had a Seadoo that was getting water in the cylinders. I had a 2 stroke outboard with a bad head gasket and in both cylinders that it was leaking both the spark plugs and the tops of the pistons where perfectly "steam cleaned" and the 3rd cylinder and spark plug looked normal.

 

[97_Sea_Doo_GTX]

So, a question I have is if it's carbs, wouldn't both carbs have to have the same issue? Seems like both cylinders have a similar problem. The only real difference between the 2 carbs is that the mag carb has the pulse line and internal fuel pump. I might be totally incorrect on this assumption.

I couldn't find anything wrong with the pump portion of the mag carb but I will check again per you suggestion. I'm taking any advice I can get! I am also wondering why it runs somewhat normally at first but gets progressively worse the longer it runs. Something seems to change as the engine warms up.

 

[emspjay]

You might want to try a new rectifier then. I had one go bad a few years ago in my 1996 GTX. It would run good the first few minutes then would not go past idle speed. Let it cool down then the same thing run good for a few minutes then back to not running past idle.

 

[97_Sea_Doo_GTX]

I'm not ruling anything out at this point. The rectifier crossed my mind. Who knows if it's ever been replaced. Maybe getting false plug color readings because of weak or erratic spark voltage?

I looked at the head and I can't see any obvious cracks. Looks like the seals were making good contact with all of the mating surfaces.

Old school single carb V8's are so much easier to deal with!! LOL!

 

[POPPS]

A poor rectifier will not produce gray plugs,,,you/we would be so lucky...if anything,,,you would get black plugs from a weak spark due a weakness in the electrical/ignition system.
Go through the carbs, with a fine toothed comb,,,80% of the time,,,lean seizures /partial seizures, (gray plugs),are caused by fuel issues in the carbs.
Both your plugs are gray'ing,,,it's very rare for the 2 micro filters to be blocked,,,so I am leaning toward the fuel pump assembly/pulse line,,,,assuming everything up stream is perfect.

 

[97_Sea_Doo_GTX]

Thanks Popps. That's where I'll start. Yes both of the micro filters in the carbs were very clean. I agree that it seems like the fuel pump is not pumping to full capacity.

Stay tuned for a report later this week...

 

[mikidymac]

You are running really rich not lean...

I don't think you are getting water in or your pistons would be perfectly clean from the steam.

 

[97_Sea_Doo_GTX]

Thanks for your input. I tend to agree with you having done some research this week. I also have a buddy the has years of experience with 2 stroke dirt bikes and he believes it is rich also.

I haven't had time to tear I'mdown the carbs yet. Just for fun, I started the engine up and let it run for about 10-15 seconds then shut it off. Pulled the plugs and they were extremely wet, almost dripping with gas.

Almost seems like the PTO carb is more rich than the Mag carb but both appear rich. Needles and seats will need to be inspected thoroughly. They are new and genuine Mikuni.

 

[97_Sea_Doo_GTX]

Well, completely took the carbs apart again. Everything was clean. I sprayed carb cleaner through all passages, all 4 jets and seats and blew them out with compressed air. The tiny idle circuit ports in the throat are.still open just like when I rebuilt the carbs a couple of months ago.

Idle mixture both set at 1 turn out. High speed.mixture at 0 turns out on the mag carb and 1/2 turn out on the pto. Pop off at about 36-37 on both carbs. They hold decent pressure after pop off with no bubbles around the seat. Internal carb check valves working the way they should in both directions. All internal parts still look new

I'll get them back on this weekwnd. I decided to completely drain the fuel tank just in case i got a bad batch of gas. Bought new spark plugs again as well.

Wish me luck.

 

[POPPS]

I don't think bad gas can result in gray spark plugs.

 

[97_Sea_Doo_GTX]

I don't think bad gas can result in gray spark plugs.

Me neither but figured it sure won't hurt.

 

[jrl1644]

Maybe a leak down test? You may have good rings. But have leaky seals, thereby weakening your pulse line?
Good luck with the hunt.