Jet settings

[Subjockey]

Hi everyone,
My 1996 seadoo gtx was not idling before so I decided to set the low speed jets back to factory settings, I currently have them set at 1 1/4 turns on both low speed jets, when I start the jetski it starts and builds up rev's up to about 4500 rpm and then dies, when I pull the spark plugs they are wet, would this be that the jets are too much and need a bit less?
Thanks in advance

 

[vettepilot_6]

exactly what did it do before you adjusted jets? did it run and cut out as well?

 

[Subjockey]

Yes before I adjusted it it ran and revved good but would not idle,

 

[Subjockey]

It would die if you didn't give it at least a little bit of accelerator.

 

[vettepilot_6]

I would check for air leaks on manifole etc ..first

 

[Dennis]

I would check compression.

 

[AdamXP800]

I agree with a possible air leak.


Long live the 2 stroke Seadoo!

 

[manolocross]

Gray fuel lines???? Carbs are clogged... Complete fuel system overhaul needed. Don't try to run it like this! The engine will be destroyed!

 

[Sportster-2001-951C-Stock]

All of the above are possible, and good suggestions IMO. If the plugs are wet with fuel, it kinda makes me think your carbs are flowing too much fuel at idle and it's flooding out at idle. Dirt, goo, and trash from decades of use often causes this symptom.

 

[Subjockey]

I just tested the compression, i have 150psi in the front and 60 psi in the back. I still have the grey fuel lines and I am going to replace them with new ones and clean the carbies.
thanks

 

[vettepilot_6]

I just tested the compression, i have 150psi in the front and 60 psi in the back. I still have the grey fuel lines and I am going to replace them with new ones and clean the carbies.
thanks

60psi? think it needs a rebuild....

 

[Sportster-2001-951C-Stock]

60psi is a dead hole, repeat the compression test but it sounds like you have cylinder damage and this motor should be torn down instead of run, b/c the damage will accelerate and become more expensive.

 

[Dennis]

Your welcome.

 

[Subjockey]

I pulled the carbs off and it turns out both jets had fallen out in the time i was trying to start it before i found out about the compression. not sure why the spring didnt keep them firm when they were not heaps further out than recommended setting. Anyway the more important question is what factors play in compression, parts of the rave valve, exhaust manifold leak, etc. I would like to explore all things before I pull out the engine and rebuild it, and if I do I will clean and fix all components so its a dream to have once its all done

 

[Sportster-2001-951C-Stock]

I think this is the 717 motor, thus if you'd like to lay your eyes on the reason the one cylinder is only blowing 60psi, then you have the option of removing the exhaust and inspecting the piston skirt from it's sides, or remove the cylinder head to inspect the cylinder from the top.

Arguably, it might be easier to remove the cylinder head but personally, I would remove the exhaust pipe for the piston inspection and go from there.

If this was a RAVE motor like the 787 or 951, you can easily inspect the piston skirt by removing the RAVE valve and looking through the RAVE port.

Double check your work though on the compression test, you may have had a leak or something if you didn't screw the compression tester in completely.

Edit: Oh wait, sorry for any confusion... I think you said your motor is the RAVE type, so in that case remove both RAVE valves and inspect the piston skirts for physical damage.

 

[Subjockey]

the engine is a 787cc and I checked through the rave valves and the back piston has a few marks on the side but the front one hasnt. and I checked the compression twice on both and it came up same reading both times.

 

[Sportster-2001-951C-Stock]

the engine is a 787cc and I checked through the rave valves and the back piston has a few marks on the side but the front one hasnt. and I checked the compression twice on both and it came up same reading both times.

Can you see scoring on the cylinder wall as well? The damage you see on the piston likely explains why that cylinder only blows 60psi, those are scoring marks and the piston rings aren't sealing the pressure.

Can you maybe snap a picture through the RAVE port and post it up? Also, you can see the piston condition better through the exhaust port once you've removed the exhaust pipe. The head is easy to remove as well, but you cannot see the side of the piston from the top.

 

[Subjockey]

Hi everyone,
sorry for the delay for the ones who are helping me with my problem, but I have being removing the head off my jetski, I have attached a photo of what I found.... Yea not the best... but at least I found the problem. I would say the chunk missing out of the piston is why I was only getting 60psi and Im surprised I was getting that. I think the cause of this is the old owner bypassed the fuel filter! and when I bought it I put one on. but anyway it has the grey fuel lines and that would mean the carbies are clogged from what I read. So the cylinder must of gone very lean and then detonated. there is only very very minor scoring, believe it or not the front cylinder with 150 psi has more scoring than the back, so I should be able to just put a new cylinder and rings shouldn't I? Thanks guys much appreciated!

 

[AdamXP800]

Well id say there's your problem. The problem with just throwing a top end on is the pieces of that piston could be down in the bottom end. Other more experienced members will chime in soon.


Long live the 2 stroke Seadoo!

 

[Minnetonka4me]

Yup it has to be fully taken apart and checked. Usually that kind of damage is from running bad gas or way off timing.

While you are rebuilding, rebuild the carbs, change the fuel lines, pull the fuel tank and clean it.

 

[Sportster-2001-951C-Stock]

Looks like a fueling problem to me too, I see outboard 2-strokes that look like that often. Bad fuel and/or plugged carbs cause lean detonation or octane detonation, and it doesn't take long, same result, the piston overheats and the oil film breaks down causing scoring too. The most recent one was an injected merc outboard, the piston was in the bottom of the crankcase burned and broken in hundreds of pieces.

 

[Dennis]

What Sportster and Minne said. Lean fuel condition burned off the edge of the piston. Id be willing to wager that the piston damage is on the same side as the exhaust port.

 

[Subjockey]

What Sportster and Minne said. Lean fuel condition burned off the edge of the piston. Id be willing to wager that the piston damage is on the same side as the exhaust port.

believe it or not its actually on the intake side, and do you guys think I will get away without boring the cylinder seen its only a little amount of scoring?

 

[Sportster-2001-951C-Stock]

believe it or not its actually on the intake side, and do you guys think I will get away without boring the cylinder seen its only a little amount of scoring?

You might end up with a money pit if you're not careful. A new piston(s) and rings might work but I have serious doubts about your crank rod bearings b/c I'm pretty sure they are contaminated with aluminum from the piston. 2-strokers in general, and these 951 motors in particular, are rather famous for being unforgiving and the crankcase can be ruined if a connecting rod is broken.