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High speed sputter....

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tkarvelis

tkarvelis

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High speed sputter 95 GTS....

I have have working on this seadoo, and I have it ready to hit the water.... except for a sputter from 2/3 throttle to full throttle. It will not do it every time from idle to full. It sounds like it is running lean. Right now low speed is set for 1 1/4 and high speed has been adjusted from closed to 1/4 open. The plugs are getting a nice light brown color.


I have a video, but I can not get it to post from my phone. I will have to post it later.
 
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You can't tell much from running on the trailer aside from whether or not it runs and both/all cylinders fire. If in doubt splash it and be prepared to make final adjustments in water.

Set idle speed a hair over 3000 first, mine idles about 3500 out of water b/c I like a high(er) idle.
 
Here are the plugs. These are from running on the hose, and also running on the trailer in the lake. They look good to me. The porcelain is starting to turn a dull tan.


86.jpg



87.jpg
 
All the fuel lines and vent lines have been replaced. I had a meter on the battery and it is charging 13 - 14 vdc. I am not sure how easy it is to pull the MPEM to access the rectifier wire. It appears that I need to pull the oil tank on the GTS.
 
I had the seadoo in the water (strapped to the trailer), and it was running nice to about 2/3 throttle. It had good power, and wanted to push a F-250 parked up hill on the launch. I get the feeling it is running lean, but the water jacket is holding around 150 - 160 F with a IR thermometer, so it is not excessively hot. Plugs look good. I just don't want to blow a piston.

I did notice it does smoke some, but I still have premix in it since I was not sure the injectors worked, which they do.
 
I think if you're on the trailer there's a good chance at 2/3 and more throttle your jet pump will be sucking air under the hull and ventilating the impeller thus might be unhooking and not acting normal.

If too lean in the high speed it will tend to lean surge and giving a little choke will add some fuel to make that up. You have high speed adjusters, you could crack them open 1/4 turn and should notice a drop in RPM at WOT. Once you see a 50RPM drop at WOT you know there's enough fuel. Too much fuel will tend to fould plugs a little quicker and not rev quite as high.

Conversly, if the jet pump is in good shape and you have the correct impeller, the ski should not be bumping the rev limiter. Pump condition aside, I would take bumping against the rev limiter as a possible sign of being too lean.

My plug insulators start off yellow for the first 30 minutes or so, then progressively darken to cardboard brown. Grey is a sign of too lean, IMO. Black is fuel soot.

That plug looks pretty decent to me too. But it needs to get progressively darker and not remain tan. We want them to foul on hydrocarbon deposits eventually, not aluminum deposits.

You can watch piston wash as well, there are probably some photos floating around.

But if by opening the HS mix screws 1/4 you should expect about 50RPM or more drop.

2-strokes run like a bat out of hell right on the hairy edge of lean-seize.
 
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The pump has been rebuilt. New bearings and wear ring. Clearance is good. I will adjust for the rpm drop. This is how I have adjusted small engines and string trimmers for years, but I was alittle concerned about doing the same on this engine.
 
As sportster said you need to get it out and ride it. Running on the trailer even at WOT will not tell you anything about top end jetting.
 
tkarvelis said:
This is how I have adjusted small engines and string trimmers for years, but I was alittle concerned about doing the same on this engine.
Click to expand...

Yep, can't do it on the trailer though b/c you're going to run into impeller ventilation issues but aside from that they do actually rev out higher when the ski is moving through the water at speed. Sitting still on trailer or tied to a dock or tree even, isn't my idea of a good set of tuning conditions.

So I suggest setting the mix screws to factory setting and going for a WOT ride. If the motor runs strong and doesn't miss, stumble or hesitate but you want to add a little more fuel (a strategy I can appreciate) then shooting for a 50RPM WOT drop should get you safely on the richer side of happy.
 
From your description in the first post along with the video, it sounds like you are hitting the rev limiter. The engine will hit the rev limiter very quickly with no load on it. As others have said just go ride it so that the impeller is loaded and you can make a better diagnosis.
 
Well I took it out on the lake yesterday. I ran in, and I did not notice the sputter like i had in the video. I grabbed my daughter and we were riding it for a while. I would guess 1 1/2, and it died. We were WOT and dead. I tried to restart it, and it acted like the battery was dead. We sat on the lake for a bit waiting for a boat to tow us, and i tried again to start it. This time in cranked slowly but would not start. I got towed into the docks, and I put it on the trailer. I had a DMM with me and measured the battery voltage. 12.5 with no load. I tried to start it, and she fired right off.

So now I need to figure out if I seized it, and when it cooled, the rings compressed, and it allowed it to start.

Would a compression test prove anything?

I am going to start it on the hose, and measure the charging voltage. I am hoping for a bad rectifier, and not engine damage :)
 
A compression test will always give you some info to go on. What do the plugs look like now? Sorry you had to be towed. That s#cks especially with family on board.
 
JMHO
You seized it because you are running slightly lean (plug in pic). I bet you do a compression test and it will be fine. Those 657 engines are tough as nails. Did the same thing to one I had several years ago. As soon as it cooled off did a compression test fixed the lean condition an away we went. That thing is still running today. I see it on the lake often.
 
PTO side


169.jpg


Mag side

170.jpg


I do not like the plug color.

I tried to do a compression test, but the battery would not spin the crank much. I had a compression gauge on it, and got to 122 with throttle wide open. I don't trust those numbers, bc of the weak battery.
 
Well I tried to turn the flywheel by hand and no go. I sprayed oil into the cylinder hoping if the rings were tight a bit of oil would loosen them.

I thought about the pump or through hull bearing, but I rebuilt the pump, and I can turn / rock the flywheel a bit each way.
 
If you tear the top end off, look and see how much oil is puddled in the bottom end, should be enough to touch the crank wheels. Those plugs are too light for 1-1/2 hours so something wasn't right.

And, was the oil injection pump linkage correctly calibrated or running pre-mix?
 
I will pull the top end off hopefully Wednesday unless my daughter's softball games are rained out, then I will do it sooner. There was pre-mix in the fuel, as I was not sure the injectors were running correctly. I had tested them on the bench, and bled them. I have a full tank of oil.

I need to decide if the ski is worth putting more money in, or part it out... I am looking at around $300 for a top end rebuild kit, and whatever it will cost to have the cylinders bored and polished.
 
Well I pulled the head off, and the walls look perfect... It is not the engine but the jet pump. I rebuilt it, and I have the 1/5 hours ride time, plus running it at home for a bit, in at the lake to adjust the carbs...

Time to rebuild it again.
 
That's good news. I'll stand behind the HS fuel mixture being adequate when the carbs are setup as per factory spec but it's acceptable IMO to add a bit of fuel if you desire.

That is, provided there's not something wrong such as an air leak somewhere and the engine runs strong like it should.

At least they aren't grey......... Those plugs should darken up though, if they don't try to feel for a lean hesitation while running off the HS circuit, there shouldn't be any mushy lean feeling.

I guess the oil leaked out of your pump hub/stator. A hurt pump can make the engine feel sluggish, not feel quite right and run a bit hot so perhaps that explains why the plugs haven't gained much color also the reason for your earlier concerns about poor performance.

Good luck! :)
 
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