should I do a top end rebuild?

[andrewterri]

just bought a ski for cheap with carbs needing rebuilt. I opened the carbs and were completely dry with a little rust on couple screws. ordered OEM Mikuni rebuild kits and new needle and seats for both along with new jets. All sizes were ordered to match factory which I confirmed was what was in the carbs. waiting on parts and thinking about doing a top end rebuild. I pulled about 125 and 127 on cold engine with ambient air temp of 43F. would you guys just run the ski or go ahead and do the rebuild now? thanks for your help and thoughts. no one has a machine shop to do the work where I live so any suggestions where I can sent them too would help. thinking I paid 75 on other skis to have them honed. leaning towards it just because I enjoy working on ski's it's my escape from nagging wife and crying baby

 

[mikidymac]

I would get the ski to fire then with a new strong battery and the throttle held wide open check the compression again.

The compression could come up a little once any rust is knocked off the cylinders.

What ski did you buy?

580-787 should have 150 psi compression to be perfect 120 is time for rebuild.

951 should have 130 psi to be perfect and 110 is time for rebuild.

I use Group K for all my machine work and they charge $55 per cylinder to bore and piston match.
OEM pistons are the best and I use WSM for cheap stock rebuilds. Never had a single issue in 25 years with WSM pistons. I use only OEM in my personal skis I will ride hard.

 

[andrewterri]

The ski is a 96 GTI so it has the 720. I would put a picture up from my phone if I could figure out how to do it. Never been able to get it to size correctly. Anyways, PO said the ski has been in the family since new and has slowly started running poorly and getting harder to start. PO stated he cleaned the carbs and wasn't any better. His brother was into the seadoo's and has since married and moved out so he just wanted to sell it. Looked at machine and saw the grey lines. asked how he cleaned the carbs and he said he just shot carb clean down the throat. After seeing compression clearly the carbs are plugged. Only paid 550 and it has original matching seadoo trailer. Ski always stored indoors so its in great shape. Bought is for my daughter so we are working on it together. ordered all new mikuni rebuild kit along with new needle and seat as well as jets. carbs were completely dry when I opened it up. Just thought about top end while its already apart and winter. of course got new fuel line, oil injector line, fuel and oil filter, water separator filter and o-ring, plugs, 2 gallons seadoo oil since unsure whats in there, and a couple other things I cant think of right now.

 

[mikidymac]

Sounds like a great start.
I wouldn't bother with a top end yet.

 

[andrewterri]

thank you for the advice. I will finish the carbs when the snail-mail gets it here and just run it

 

[andrewterri]

 

[andrewterri]

finally figured out how to attach a photo. only took 6 years

 

[mikidymac]

Wow, that thing is super clean.

Try the tapatalk app for your phone. By far the easiest way to post pictures.

 

[andrewterri]

Thanks for the app info I get download that. I thought is was really clean for the year. when I saw 120 compression and not zero in a jug I could not pass it up for just over 500 bucks.

 

[mikidymac]

THat GTI is not the fastest ski but they are probably the most reliable ski Seadoo made and very fun for what they are. Probably the best entry level ski you could have found.

 

[tkarvelis]

Make sure to clean / replace the fuel selector. It will clog and or send more crap to the carburetor.

 

[andrewterri]

Thank you tkarvelis. I plan on ordering one. I cleaned mine on the 95 but was not really worth it for the cost.

 

[mikidymac]

They will typically start to suck air after they have been cleaned. Not worth a seized engine over.

 

[andrewterri]

Thank you. I am I just need it to warm up here so I can replace the fuel lines. In my garage it is 45 degrees and the lines are rock hard even the new ones are very stiff. Tomorrow should be 55 and 67 on Friday.

 

[mikidymac]

Sorry. Here in California it was a chilly 65 degrees today. Almost had to wear a sweater.

 

[andrewterri]

Is that New California or old? LOL Must be nice. I miss the weather out there. I was in the Marines and stationed there. Hopefully we can stay warmer in Oklahoma. The lake temp is 32. We live on the lake and that's all the family does 5 or 6 days a week in summer. We get serious boating fever around this time of year. Cant wait for that first trip. I really appreciate your help with this Seadoo. My daughter said than you as well.

 

[mikidymac]

No problem. I guess I would be in old California. 50% love for the state and 50% hate so I guess it doesn't matter.

Glad to help.

 

[IDoSeaDoo]

If I were you, I'd consider pulling the head and inspecting the pistons. You can see the ring-end gap on the top ring, and if it's looking large, your rings are probably toast. You may be able to just put in new rings and rod bearings and continue using those OEM pistons, if they're in good shape. If everything looks good, you can put the head back on like nothing happened. There is no head gasket, rather just two O-rings. They can be reused as long as you apply the proper sealant, as specified in the manual. It's this red goop stuff that never quite hardens. As always, I recommend cleaning the bolts and chasing the threads on marine engines, and use blue Loctite to make sure they don't wiggle out.

As mentioned earlier, great looking ski. Very good shape for the year. Every time I get a new ski, I make sure to check that coolant drain line that comes off the T-fitting at rear of the cylinders. I had one clogged with sand, and it was impossible to tell by just looking at it. Try and flex it at the lowest point. That's where the sand tends to build up. If this is blocked, it'll still run, but the extra heat will degrade the motor much faster.

 

[andrewterri]

Thank you for the tip. Ya that sealant for the head makes a mess. I think its called aerobatic sealant. Thinking about doing that but a little paranoid. Friend did a top in job last year and can not get the head bolts or jug bolts to stay on tight. ski keeps leaking water at the base gasket. On his ski I think seadoo only called for 16lbs on the jug bolts but after multiple failed attempts he took it to 30lbs and same problem. I am scared to death of having whatever issue he is having. I know it is very simple but seeing a problem like that will make you second guess yourself.

 

[andrewterri]

While I'm thinking about it, I now know there was no fuel or oil being injected into the motor when I turned it over for the compression test. I got about 125 in each jug with an ambient temp of approximately 45 degrees. Once I check it with the carb on and oil injector set how much will that increase the psi? will it at all?

 

[mikidymac]

It will not increase with the carbs on. I would get it to fire and run for about 20-30 seconds and give it a couple rev's. THen let it cool down and check the compression. I think it might come up a little since it has been sitting for so long.

As for your friend, he is doing something wrong or has bad parts as I have never seen one leak and overtorquing it is not the answer. Are there any cracks.

1. Make sure all sealing surfaces are clean and flat.
2. Make sure you are using the correct gasket and correct thickness to get the required squish gap on the pistons.
3. Follow the service manual exactly as to what grease, sealant and/or thread lock on the bolts.
4. Install the exhaust manifold hand tight to align the cylinders.
5. Torque the 4 bolts per cylinder in a criss cross pattern starting at 10 ft/lbs then increase this to the required torque.

For the head it is 515 or 518 flange sealant on the cylinder o-ring and then grease the threads and loctite under the bolt heads they torque per the manual. The shell and spark plug o-rings go on dry.

 

[andrewterri]

I am thinking when he had the boring work done the cylinders were either cracked and it was not magnafluxed or the jug base or casing is warped. I helped him when he brought it over to my house and I retorqued and followed seadoo's specs to the letter. When he rode it at the lake he asked me to come with him so I could be a tow boat if needed. He rode it for about 5 minutes then we could see the water coming out between the cylinder base gasket and the jugs. everytime it has happened and he tore it down the screws were rattling around loose. I told him that I think there is grease and dirt preventing the Loctite from bonding. I told him not to over tighten as it is on aluminum, of course, he said he soaked it in Loctite and went as tight as he could without cracking or stripping anything. Another example of someone treating the symptom's and not the problem. He likes to cut corners on things and it drives me absolutely nuts. Yet he wonders why our ski never has problems and runs so well with such reliability and his doesn't.

 

[IDoSeaDoo]

He might have stripped threads in the case, especially given his propensity to overtighten. He can fix this with a properly sized and inserted Heli-coil. It's possible there may have been some freeze damage. That can crack the cylinders, but it usually occurs at the top where they are thinner. I can't imagine how the case might be warped. If it overheated to that extent, there would at least be significant discoloration, if not complete physical failure. I've had a jug that someone cleaned the gasket off with a side-grinder, leaving huge grooves in the bottom mating surface. This type of idiocy can usually be corrected with case sealant, or even RTV between the gasket and the cylinder.
In your case, I highly doubt you'll face the same consequences. Just follow the book, clean your mating surfaces, but don't gouge them, and check your squish gap when you're done. That's IF you decide to pull the cylinders. I'd just pull the head first.
Upon re-assembly, I always like to chase the threads with a tap to get all the old thread locker out. I also like to coat the shank of the bolt with grease, as I ride in the salt and a lot of corrosion builds up on the shanks.

 

[andrewterri]

I will pass your information on to him. He bought the ski for him and his son to ride and spend time together. After the top end the ski ran great or 30 minutes until water got into the cylinder's. plugs were wet and water coming out between jugs and case. Thank you for the information on it as it has stumped me on what would keep causing this. I will thank you for him as well; I know he really appreciates the help. I keep telling him to find/make the time and get on here that you guys can help. I tell him I know what I know because of this forum.

 

[IDoSeaDoo]

Yea, we've all learned a lot from others' experience on this forum. I personally have put in 100's of hours wrenching on these things and am always happy to pass on some knowledge. I'd like to save people some misery if I can.