2001 seadoo gtx's....Some advice needed please

[newtomedoo22]

Good Morning everyone! New guy here asking for some advice.. I find myself in possession of two identical 01 gtx machines and I wonder what my next steps should be. Here is some background:

unit#1 has 120 psi compression on both cylinders. This measurement was taken with the machine cold, wot and with a new otc tester. I told a look inside the cylinders with a scope and there is carbon build-up on the top of the piston with small bare patches around the diameter. machine starts and runs fine on the trailer.

unit#2 has 130 psi on the mag side and 100-105 psi on the pto side. This one also has carbon buildup as the other and was tested in the same way. It also starts and runs fine on the trailer.

I have not had either of these in the water and am hesitant to do so after reading numerous threads on this forum. In one respect I would like to at least take them out and try them to see how they do before I start messing with them too much but on the other hand I don't want to cause any damage before maintenance is done.

As I see it the to do list should be:
rebuilding the carbs with genuine mikuni kits reusing original springs and replacement of fuel lines and filter with pressure testing of the carbs and fuel system
replacement of the oil lines....both machines have an unidentified blue green oil in the tanks. One of the tanks was replaced and I have a spare.
removal of the oil filter and replace the seal in the bottom of the oil tank
cleaning of the rave valves
Do not delete the oil pump but premix the gas 40:1 with seadoo oil and a dose of ring-free for good measure

The previous owner claimed to have used half a bottle of marvel mystery oil in each tank of gas, maybe the cause of carbon or are they just running lean?

I have seen on you-tube where someone removed the cylinder head and soaked the pistons with wd-40 and then lightly scraped them with a wooden scraper and light scrubbing with a scotch brite pad...Is there any point to that? May or may not affect the compression?

Guys..I need all the advice and encouragement I can get. Thank You for any and all replies..

 

[mikidymac]

The one with 130/105 has a bad cylinder and will have to be rebuilt, period.

Yes full carb and fuel system rebuild. Get the correct oil in the and replace the inline oil filter and little oil lines from the pump to the intake manifold.

No reason to premix in addition to oil injection and no reason for any fuel additives except fuel stabilizer for storage.

 

[newtomedoo22]

Mikidymac , Thank You for your reply (The one with 130/105 has a bad cylinder and will have to be rebuilt, period.) Yes, I figured as much! I would like to practice the modifications/repairs on the unfortunate one before I tackle the better one.I understand a top end rebuild is no good on this machine, That I could have done. A full rebuild is beyond my abilities though so I guess a refurbished engine replacement I could handle.

I live quite near SBT, apparently not everyone's favorite but easy for me to aquire an engine from

 

[mikidymac]

Yes on SBT for an engine. But do not use their carb kits.

 

[newtomedoo22]

Since I’m going to be removing the carbs and removing/replacing the fuel lines,oil tank and oil lines should I remove the exhaust? Removing it seems straightforward,I have the special flat wrench as well. Removing the entire exhaust looks easier than just removing the tuned pipe. I have the Covid too at the moment so I have plenty time to contemplate and study the shop manual

 

[mikidymac]

I don’t suggest messing with the exhaust.

 

[newtomedoo22]

Ok.. Covid be damned I got that carburetor out without touching the exhaust. Dreaded green goo on the hoses. Now I can finally see where the little oil lines go! If it wasn’t for mikidymac’s write-up on rebuilding the carb I probably wouldn’t have thought to try

 

[Grim]

From my experience ,I did remove the entire exhaust. so much easier to uninstall and reinstall carbs that way, just don't split the exhaust at all.

 

[newtomedoo22]

Boy oh boy, I had no idea what I was getting myself into when I bought these ski's. So far, I have removed the gas and oil tank + lines. I have rebuilt the rave valves and the carbs are mostly done (I had to order the needle and seat assembly's) I told my wife when I bought them that I wanted to learn how to work on jet ski's, so I guess my wish is coming true! I am practicing all of this on my low compression machine which will need a new engine or major work that I have yet come to terms with. Tomorrow I'm gonna drain the crankcase oil and see what that looks like and reinstall the gas and oil tank+ lines.

 

[newtomedoo22]

Ok,so an update on my progress. I cleaned the fuel tank. I removed and replaced the fuel tank selector switch and fuel lines. I did the same with the oil tank and lines. I rebuilt the carbs with mikuni kits and set the pop off pressure on each to 20 psi. I did the 10 psi leak test. I reinstalled everything, added 5 gallons of gas at 40:1 because the oil pump seems to be taking its time to get oil to the cylinders. Its creeping but is going. I started it up and it runs like a scalded cat. 5000 rpm or so out of the water. Obviously that's not right but I'm not sure what I did wrong. I didn't mess with the throttle cable adjustments. High and low speed screws are where they belong. Idle adjustment screw is backed off as not to make a difference. Any ideas other than remove the carbs and try again? The needle and seats where not original mikuni but I couldn't find any...maybe I should just reinstall the old ones?

 

[newtomedoo22]

Another curious thing, just for hell of it, I removed the cylinder head and cleaned the carbon from the pistons with a mild scotch-brite pad and some wd-40 because I saw someone online do it. Gave me an opportunity to inspect the cylinder walls as well. Everything looked fine. I had the raves out so I could also look and get a small glimpse of the rings and they looked ok too. I installed a new gasket and used some copper gasket spray before retorquing it to specs. Before I cranked it up I tested the low cylinder and I got 95 psi, not what I was hoping for. I decided to start it up just the same and when it was done running like a banshee and warm, I decided to test it again. This time the low cylinder tested at 120 psi? What gives? Wishful thinking or something else?
Update...I retested it again this morning cold and it still tests 120 psi.

 

[newtomedoo22]

Ok,so an update on my progress. I cleaned the fuel tank. I removed and replaced the fuel tank selector switch and fuel lines. I did the same with the oil tank and lines. I rebuilt the carbs with mikuni kits and set the pop off pressure on each to 20 psi. I did the 10 psi leak test. I reinstalled everything, added 5 gallons of gas at 40:1 because the oil pump seems to be taking its time to get oil to the cylinders. Its creeping but is going. I started it up and it runs like a scalded cat. 5000 rpm or so out of the water. Obviously that's not right but I'm not sure what I did wrong. I didn't mess with the throttle cable adjustments. High and low speed screws are where they belong. Idle adjustment screw is backed off as not to make a difference. Any ideas other than remove the carbs and try again? The needle and seats where not original mikuni but I couldn't find any...maybe I should just reinstall the old ones?

Uh, no they weren’t… I musta hit the low speed screw on the pto side when I was installing the carb.. put that back where it belongs and now we she’s 3000 rpm on the stand.

 

[newtomedoo22]

Ok,so an update on my progress. I cleaned the fuel tank. I removed and replaced the fuel tank selector switch and fuel lines. I did the same with the oil tank and lines. I rebuilt the carbs with mikuni kits and set the pop off pressure on each to 20 psi. I did the 10 psi leak test. I reinstalled everything, added 5 gallons of gas at 40:1 because the oil pump seems to be taking its time to get oil to the cylinders. Its creeping but is going. I started it up and it runs like a scalded cat. 5000 rpm or so out of the water. Obviously that's not right but I'm not sure what I did wrong. I didn't mess with the throttle cable adjustments. High and low speed screws are where they belong. Idle adjustment screw is backed off as not to make a difference. Any ideas other than remove the carbs and try again? The needle and seats where not original mikuni but I couldn't find any...maybe I should just reinstall the old ones?

I reinstalled the old ones, setting the pop-off was much more consistent.

 

[mikidymac]

951 should have the idle set on the trailer to 2,800 not 3,000 rpm.

 

[newtomedoo22]

Took it down to the ramp, stuck it in the water and started it up. It runs good on the trailer. I revved it up and it ran well. It did have a very few small bubbles of water developing from the top corner of the mag side cylinder head. I assume I don't have a good seal. I removed the plug and no water shot out, so I guess that's good. I will let it cool down and try retorquing the bolts. More than likely, I will need to do the cylinder head gasket again. Not knowing what this engine is supposed to sound like, I hear an occasional clanking sound, don't know where its coming from or if its normal. please advise.....Thanks

 

[newtomedoo22]

My tinkering with the first one paid off because I placed the second one on the stand( I made one out of 2x6’s) today and had the raves,gas tank and lines, oil tank and the carburetor out in a jiffy. I’ve ordered all my parts and know what to do. The old oil tank had leaked about a gallon of blueish oil all into the bilge, that’s gonna be a mess to clean up. I have a new tank and seals coming.

 

[newtomedoo22]

So I re torqued the head bolts to 25 ft lbs and took it out for a quick spin. It ran really well and seemed to have no acceleration,idling or vibration issues, nor any more bubbling from the head gasket. I hit 5000 rpm ( Don’t know the maximum rpm because I didn’t try) but the speedo isn’t working so I don’t know how fast that was but it felt fast. My first time on a jet ski in about 25 years so I took it kinda easy. Now to get the second one redone.

 

[Lothsahn]

Not sure about the 951, but my 787 and 587 both don't make any sort of clanking sound. There's a bit of rattling at idle from the jet pump from basically all of them, but once you give it any RPM at all, it should completely go away.

 

[newtomedoo22]

That may be what I’m hearing and at rpm it stops. Once I get the 2nd one going I should know right away what’s normal and what’s not.

 

[newtomedoo22]

A leaking oil pump has me waiting on parts (used oil pump from e-bay) since no new pumps or rebuild gaskets seem to be available. The top plate with 2 screws and a formed o-ring or deformed o-ring in my case is the problem. It was drip, drip, drip of almost 70 bucks per gallon sea-doo oil. I wonder if I could seal it with some permetex black gasket maker? Gonna try the replacement pump from the land of freshwater use first (Minnesota)and see how that goes..

 

[newtomedoo22]

Another curious thing, just for hell of it, I removed the cylinder head and cleaned the carbon from the pistons with a mild scotch-brite pad and some wd-40 because I saw someone online do it. Gave me an opportunity to inspect the cylinder walls as well. Everything looked fine. I had the raves out so I could also look and get a small glimpse of the rings and they looked ok too. I installed a new gasket and used some copper gasket spray before retorquing it to specs. Before I cranked it up I tested the low cylinder and I got 95 psi, not what I was hoping for. I decided to start it up just the same and when it was done running like a banshee and warm, I decided to test it again. This time the low cylinder tested at 120 psi? What gives? Wishful thinking or something else?
Update...I retested it again this morning cold and it still tests 120 psi.

So here I am a year or so later and each machine tests out at 120 psi on all cylinders without having done anything other than what was described above. I may have had issues using the tester at first, I started off with a cheap one and then went to the OTC. They are running well, I had to replace a steering cable on one and I'm in the process of sorting out a speedometer issue on the other. Keeping my fingers crossed for many more good days on the water.

 

[newtomedoo22]

OK, so here I am almost a year later from my last post, and they are still running strong! In the meantime, I have rebuilt both jet pumps, added stainless props and replaced steering cables on both, speedometers are all fixed and life is good at the moment! Let's hope things stay this way!