2001 GTX rebuilt top end, but ate another piston after 1 tank of fuel

[kleake]

I'm new to PWC's, I've ridden them, but never really worked on them. I do have plenty of mechanical abilities as I work on lots of other things uncluding cars, motorcycles, boats, and pretty much anything else.

I have a 2001 GTX with the carbed version of the 947/951 engine. Original owner let it sit, then got it running but it lost all compression in 1 cyl. Took it to a shop who replaced the jug and piston and got it running. I purchased it before it was actually lake tested. When I checked it out, I found that he put the gasket on wrong between the exhaust manifold and the pipe, allowing water to fill the cyl and spray into the engine bay when I hooked it to the hose. Fixed those, then found the carb filters were plugged due to the cheap fuel hoses. Fixed that and a few other minor things.

First real trip to the lake thinking all was good and after a 5 minute ride, the hi temp alarm goes off and I immediately shut it down. Pull the seat and it's SMOKING hot!!! Like boiling water hot! I see it blew the hose off the top of the head and there wasn't a gasket on it, so I had some zip ties handy and zip tied it on. Let it cool for a while, fired it up and it ran ok for a minute but then fouled a brand new plug. Swapped it for a spare and it ran great. Rode about 3/4 tank of fuel fine, then it fouled another plug in the opposite cyl. Swapped it with my last spare and it ran great again. The plugs were a medium brown color so it seemed to be pretty close to the way it should run and we wasn't running it hard since it was still not 100% right. Refilled the tank and used maybe 2 gallons after the refill and it locked up. Pulled the plugs and I see metal slivers on one of them.

The oil resevoir started at full and had dropped about what I expected and when starting it there was smoke, but that went away after warming it up good. Exhaust smelled basically like a dirtbike so my best guess is the oil injection was working, however maybe not as good as it should. Engine ran good and had plenty of power all day. I did feel funny hesitations once in a while or maybe some surging, but it was more like fuel starvation or a plug trying to foul. Every time I replaced a plug it ran really good for a while.

1st, what might the problem be? Did the previous tech do something wrong (I did find several things that weren't right, but I fixed them all I "think"). Is the oil injection not working right? What else?

2nd, where is the best place to get the parts to replace the top end again?

Thanks in advance for any info.

 

[Sportster-2001-951C-Stock]

My 2001 carbureted 951 used to blow 132 psi of compression, now it blows 123psi but still runs fine. It's possible you may have experienced a partial seizure when the engine overheated, leaving some piston aluminum smeared on the iron cylinder wall. It's usually downhill from there.

It's also important to use the correct type of oil, API-TC rated full synthetic. TCW3 marine oil cannot take the heat generated by these motors.

RAVE exhaust power valves vales might be dirty and sticking.

There's a procedure for calibrating the cable linkage of the oil injection system in the factory service manual, those manuals are available in many places on-line and very worthwhile having one.

There are some very small passages in the ALUMINUM carburetor known as pilot bypass transition holes, it's important these aren't plugged even partially, by light corrosion or debris.

My carbs were too lean off idle up to about 70% throttle where the main venturi begins to flow even after cleaning them thoroughly twice there was still a wide flat spot causing lean hesitation.

I decided to rejet the low speed circuit so I bought a set of #77.5 and set of #80, the #80's were the first I installed and they eliminated the lean hesitation completely, there's just a bit of rich 4-stroking around 3000RPM that's barely noticable once fully warmed. I haven't tried the #77.5's but I think they might've been large enough.

Also replaced the metering needles and seats, a carb this age isn't fresh unless these are replaced, IMO, b/c the rubber tips are impregnated with graphite lubricant that wears off and the rubber tip becomes grooved over time and prone to sticking in the seat as well.

I wanted to make sure the third time was a charm, so also installed 80 gram metering springs instead of the 95 gram springs. This drops the pop by just a few pounds. Probably this wasn't necessary.

The heat-soaked start is great, idle is great and operation is nowhere near being too lean, safely rich.

Eventually I intend on going back to the 95 gram spring and giving the 77.5 jet a whirl, but it runs pretty sweet the way it is, so no rush.

Running too lean will cause detonation and eat pistons pretty quickly, better to be on the rich side.

SES will be my 1st vender of choice, or Full Bore perhaps, when the time comes my 951 finally needs reciprocating assembly work. Don't forget to chamfer the ports to avoid snagging rings on the sharp edge, lots of machine shops don't chamfer properly or at all, I guess. An overbore might require trimming the RAVES shorter, there's a clearance spec.

Also, don't forget to check/top off the balance shaft oil reservoir, I couldn't see any oil in mine when I first brought it home so I filled the cavity to within 1/4 inch of fill hole using mercruiser high performance gear oil despite the carbed motors are filled with 30wt, the later fuel injected DI version is filled using gear oil so that's what I decided to use.

Good luck.

 

[kleake]

Wow, great info, thank you!!!! Way more detail there than what I ever would have thought to look at. I know basic carbs and how all they work, but it sounds like there may be more to these than I guessed.

I pulled the head tonight to take a look and see the damage. It looks like a few chunks of piston made their way to the top of the piston. You mention detonation. I was running 87 octane because that's what I had and didn't see that it needed 91 until after it was full. I didn't hear any detonation, but as loud as these are then I would imagine it's hard to tell. Would that have caused this that quickly? The cyl walls had a thin oily coat on them and were not scuffed from being dry, so I'm just guessing that wasn't the issue. Seeing piston chunks wasn't too bad, but seeing steel slivers and shavings tells me i'm likely going to need a new jug correct?

 

[Sportster-2001-951C-Stock]

I run 87 octane in my 951, the minimum allowed according to the 2001 owner's manual I have. No differences were noted when I tested high octane. I don't run long WOT blasts of more than a minute, long blasts are motor eaters

You'll need a crank too, it's dusted with aluminum and the bearings are contaminated. A broken rod leads to a windowed case, so you sorta got lucky b/c there's more than an even chance the rod breaks.

Hopefully the cases are in good shape.

Any warranty on this, it's a reman no-fault engine maybe?

 

[SabrToothSqrl]

Since your new to the PWC world, we won't hold it against you However with a 14 year old engine... doing just the top end... especially on the high strung 951 won't end well. If it was 1-2 years old, maybe 4, you could get away with that, however what usually happens is similar to what happened to you... if it's not completely overhauled, it goes boom within a tank or two.

I'd find a rebuild shop that offers a no fault warranty, and slap the engine back in it

 

[kleake]

Definitely no warranty on this one. The guy who did it "claimed" he knew how to rebuild them and is just a small time shop so he pretty much washed his hands of it. I wouldn't mind doing the full rebuild myself, but honestly I just don't have the time to tear into it more than a few small things. (too many projects at the moment and didn't really need another one) I could do the top end without much issue, but after finding what I did, my concern was exactly as you mentioned. How hard is it yank the engine out of these? Just thinking of trying to save a few hrs of labor from a shop, but it's probably best just to bite it and let them do it all to allow them to tune it as well. Any idea what I should expect to pay? I know if I do it myself i'm probably looking at ~$500 in parts, so i'm guessing around $1200-$1500?

 

[SabrToothSqrl]

Reinstalling the pipe is a bit of an art, but if you know what needs done, I can remove an engine in under an hour or two and reinstall in 2-3.

SES is around $1k for a 951 w/a 2 year no fault warranty, and they include the gaskets you'll need for the pipe. I'm not sure if they include carb gaskets, it's been a while since I've had to order an engine.

Many shops/dealers won't touch a 14 year old ski. They'd rather sell you a new one. When you take a $1500 engine + $1500 in labor, you're already at the price of the whole working ski...

If you need an engine NOW SBT does a swap service.

 

[kleake]

I understand what you are saying, but help me with the acronyms so I follow completely.

SES=Standard Engine Swap? For $1k I would be willing to do that if it comes with a warranty.

Who is SBT and do you mean a swap service of the engine only?

I would like a turn key, but not at the price of $3k.

The pipe I can see is bit heavy and awkward, but i've unbolted it to fix the gasket on the engine side as well as move it out of the way to clean the filters on the carbs. The large clamp is a little finicky, but wasn't bad. I didn't remove the pipe completely as it looked to be a challenge to wiggle into the right position though.

 

[Spimothy Leary]

SBT -= short block technologies out of clearwater FL, they sell thousands and thousands of pwc engines. I have done quite a bit of business with them, i'd rank their workmanship to be somewhere between 7.5 and 8 out of 10.

you basically order one from them, and return your's in the box as a "core".
Two nice things about SBT,
1) order today, engine will arrive ASAP, like a few days at most.
2) No Fault warranty, if the engine fails again, in the next year (or two years if you pay the upcharge for a premium engine) you can simply box it up and return it for an exchange.

SES = seadoo engine shop, quality work but they rebuild YOUR engine so it takes longer, and they have earned a reputation for sometimes taking longer than promised, in other words, summer will be almost over before you get it back.

the pipe... its a PITA, no better way to say it.

 

[kleake]

I like the idea of SBT. Quick, easy, no fuss, etc. and $1200 is about what I would think would be fair to save me some effort. I also noticed they have a top end kit for $500. This would save me $700, but how bad do you think the bottom end is? Could it be a dissasembly, clean it up, make sure there are no left over fragments and I'm good to go or might I run into replacing the crank, bearings, etc.? Of course I am looking for the cheapest method, but also the easiest, isn't that the hard part, getting the best of both? lol If it was the end of summer I might be happy with the SES, but at this point in the summer, quick is good. I was planning to get this thing running and then sell it, but my daughter took a liking to it so I decided to keep it for a little while, and now this. I've always wanted one, but just didn't want another project. I kinda got sucked in, so I might as well enjoy it right!

What is the hard part on the pipe, i'm not sure if mine went back together easily and I got lucky, or if I am missing something?

Also, if I do go with the full swap, is there anything else I should do while in there? What is the baseline for setting carbs and making sure the tuning is right. Before it died it seemed to run strong, but we mostly used 1/2-3/4 throttle. That last stretch of the throttle never really seemed to have any more power.

Yes I am new to these, and apologize for the many questions. I had planned to have it running and then gather more info as issues came up, but it didn't work out like that. I appreciate all of the info!

Edit: SES has exchange engines for $999? Considering that, which would be the more reputable shop? I don't think it's advance exchange though.

 

[SabrToothSqrl]

The pipe either requires a special tool to get the bottom nut, or to remove the carbs before removing pipe and vice versa (install pipe, then carbs).

if you don't split the pipe 1/2s then the install goes a lot easier, and lining it all back up correctly is fun as well.

I've used SES several times, and for a $1k rebuild w/a warranty it's hard to beat their quality, however they rebuild YOUR engine and it can take a few weeks. He says to call to get a time quote.

SBT is a strait swap out, however I've heard (I don't have personal experience with), they use lower quality parts, as well as reduce compression to lower performance (thus slightly possibly improving reliability)

If you were in PA, I'd say come over and for some gas $ or XPS-II oil (and you are running the right oil, right?) I'd swap it while you film. I've been trying to make a 951 engine install/removal video for years, just never took the time.

Turn Key at a dealer, yes you're looking at a 2-3k fix. $1500 engine + 1k labor.

Are your fuel lines grey or black? If they are grey and say 'tempo' on them... they have to go!

Ohh, and unless you REALLY like working on your ski... again... learn from us... do the whole engine, or not at all.

I've had skis go ONE tank before it sent the crank through the case. Skip the top end route. Rebuild it all, and it will last another 200 hours

 

[kleake]

Ahhh,,, maybe that is the issue, it sounds like there is a missing bolt somewhere on that pipe. I removed the 4 in the engine end (the lower front one wasn't tight, i'm guessing this is the PITA one), one just above the carbs and one at the front that mounts it to the bracket. Then then big clamp, but that was all there was on mine.

Called SES and he is out of stock so rebuild time is 3-4 weeks. Not bad, but still longer than I was hoping. SBT is $1200 +$180 shipping or $1500 +$180 shipping for the 2 year warranty. That's starting to get steep, but it might be worth the additional year.

I appreciate the offer but I'm a bit far from PA and being my first one I don't think I would be good at creating a video. ;-) Pictures maybe. And yes, genuine XPS-II oil is what I put in.

Yep, at that price i'm thinking the dealer is out of the question since the book value is only about $2500ish on one of these.

Yes my lines are grey and i've already got them on the list to swap. Heard horror stories about those and I did get some gunk out of the carb filters while I was in there. I planned to make it until later this month and I would swap them all. Probably no better time then while the engine is out though.

Sounds like a plan because I defintely don't need any more projects. I like things to work, and I like modifying things, but I hate basic repairs anymore.

It's only got 150hrs on the ticker at the moment, probably only 3 or so since the last top end bandaid. Other than needing a good polishing it's in good shape otherwise.

 

[SabrToothSqrl]

Yea, the 951 is one of the higher performance engines, and as performance goes up, reliability often goes down.

Most people get 150-250 hours out of them. Which, really isn't bad considering that's usually over 10 years of use.

The difficult one is a NUT. there should be 3 bolts and one nut holding the top of the pipe to the exhaust manifold.

In 01 (I think) they went to a rubber gasket between the exhaust manifold and pipe, from 98-00 it was an orange paper gasket. I prefer the rubber gasket. (the manifold is different 01+ too) it has a recessed grove area for said gasket. If it's all flat, you must use the paper gasket.

Leave the exhaust manifold bolted to the engine to remove it from the hull. There's a hole in the exhaust manifold you clip a chain to, to hoist it out of the hull. I use a small S hook and a pull pall bolted to the shop ceiling.

And hey, I even have a 951 in the basement, ready to drop into a ski! I'm still looking for a ski, but telling people their blown 951 ski is worth $500 or maybe $700 with a trailer... isn't fun.

"just needs a starter" lol.

 

[kleake]

Mine has the paper gasket, but i'm wondering if the previous so called mechanic used the right one. I verified with the VIN that it is in fact an 01. I called a few shops here and cost is about what I expected so I just ordered an engine, carb kits and install kit from SBT so we'll find out.

While it's out i'm going to replace the fuel lines and put a new wear ring in it. I know it needs those. I may need to replace the oil tank as well, I think it's got a leak in it. It's pretty oily around the bottom of it after I filled it.

 

[SabrToothSqrl]

usually it's the black grommet on the bottom of the tank. over 14 years it just erodes and leaks.

it goes between the tank and the orange 90 degree plastic piece. and I think like $11 or so.

I buy a lot from this guy: https://osdparts.com/

If you remove the pipe you should see a 'cut out' area on the exhaust manifold if it uses a rubber gasket. The paper one may work, but I wouldn't suggest using the wrong one, as if water leaks in this area it will get sucked into the intake!

their shipping prices are awesome when it comes to small stuff.

 

[XP 787]

FYI I currently have an SBT 787 in my ski at the moment which is 1 year old this past March and still running great. I had a little issue with a starter I had gotten from them so I called them up and had a new one the next day. (just had to ship them back my old one) Can't beat the service.

P.S. use good oil and rebuild the carbs while you're at it.

 

[kleake]

Thank you both! I have ordered the grommet and a new start/stop button while I was at it. Definitely good prices.

The gasket is one mistake the previous "mechanic" did wrong. He never tested it on a hose.:cuss: Before I took it to the lake, I hooked up the hose and it started spraying water into the hull as well as it filled the cyl full of water! :cuss: I immediately pulled the plugs and pumped the water out as quickly as I could. Luckily I had it all out within about 10 minutes. Looked at the gasket and he had it on backwards and from what I know now, I think it should have had the o-ring anyway.

Good to hear the good results from SBT and the fast shipping and service! Planning to do the carbs and using the OEM XPS-II oil.

 

[Sportster-2001-951C-Stock]

My 2001 has the later improved o-ring type gasket on the exhaust manifold, there's a groove cut in the flange that captures the o-ring. No, a paper gasket won't work in there.

It's no wonder you lost a top end, if it was eating water.

 

[kleake]

My 2001 has the later improved o-ring type gasket on the exhaust manifold, there's a groove cut in the flange that captures the o-ring. No, a paper gasket won't work in there.

It's no wonder you lost a top end, if it was eating water.

I don't think it was eating water while we was riding it. When I first fired it up in the driveway is when I saw the water issue. Immediately fixed the gasket and tested again. Yes it had taken in a load of water, but was not running that way. I pulled plugs, cranked it over to get all water out, fixed the gasket and all was good. The mating surfaces of the paper gasket appeared to meet up correctly after that, but I don't remember a groove for the o-ring, but I wasn't looking for one either. I'll see as soon as I get to pulling it out though. Yes it is possible it was seeping some water internally, but if it was, it sure didn't show evidence of it. Damage may have already been done though. I did run almost a full tank of fuel through it before it came apart though.

 

[kleake]

Well, good news, I got the new motor all ready and setting down in the ski but I'm waiting on a couple more parts before it will be ready to fire up. While in there I replaced all of the gray fuel lines put in a new wear sleeve, fixed the grommet on the oil tank, and scrubbed the engine compartment.

You guys were right, it wasn't just a piston, it was a rod that broke. Just a guess but I think the piston skirt broke and got jammed in the intake or exhaust port causing the piston to stop on downstroke causing the rod to get yanked in half. So if I had rebuilt it, it would have been a crank, rods, pistons, and all so the new motor was truly the best solution. One of the reeds was bent just a tad but I was able to straighten it easily. The other thing I found was the half of the throttle cable that connects to the injection pump valve was broke, so i'm guessing it wasnt getting as much oil as it should have been getting, contributing to the failure. I also found the RAVE valves to be stuck in the closed position which I am sure also made it run poorly.

This thing should ride like a new ski when i'm finished with it!

BTW, what break-in method do you guys prefer on the new motor and any ballpark of what the top speed should be? I was only able to get about 48 before the engine failed but I know part of that was due to the wear ring clearance. No I am not concerned about top speed, i'm just kinda curious on how it will compare to a friends Aquatrax with a 4-stroke. It's an older one, 2006ish I think, before they supercharged them.

 

[SabrToothSqrl]

you add oil to the first tank for break-in, and ride gently. Don't exceed 3/4 throttle for the first tank.

on a 951 GTX, you should see a top around 55 MPH. Maybe 60 if it's in super good shape.

 

[Sportster-2001-951C-Stock]

When the oil pump cable breaks, the oil pump valve should be in full on flow position. At least that's what's supposed to happen.

Broken piston skirt is one of the common failures known to stop a 951, so this makes sense. For this failure I believe possibly excess cylinder bore clearance allows the piston to slap the cylinder, eventually the skit breaks from this. A seized wrist pin bearing due to broken cage might also be responsible.

Any idea what the compression was before failure?

48MPH sounds great for a 951 with stuck RAVEs, don't understand how RAVEs could be stuck if top end was recent but the wrong oil type doesn't help anything, including the wallet....

 

[kleake]

How much oil to the first tank? A standard 40:1 mix or go less since it should be getting some oil from the pump as well?
55-60 is plenty for me, I think his Auquatrax will do high 60's but it seems like it's rated at 150hp or so. Close enough for me.

Also, you were right, there was a groove in the intake for the rubber o-ring. The jackwagon that did the work previously really had no clue as to what he was doing. :facepalm:

The return spring on the oil pump valve has unhooked and you could rotate the valve all way around 360 degrees so it's no telling what position it was in. I do know when starting it up cold I did see a fair amount of smoke, but it cleared within a minute or two. Definitly could smell it so I assumed it was at least getting some. The rod moves freely in the piston, so i'm thinking the piston slap is the cause. Knowing the issues this dude had, I wouldn't doubt if he bored it too much and just went with it.

No idea what the compression was as I never tested it, but it didn't seem weak when cranking. Not a very good way to tell though.

Yep, and with the worn wear ring it had a lot of cavitation getting going (struggled to plane out with 3 people on board) but seemed to have decent traction at speed. It never really climbed to the top revs though. But yes, the valves were stuck and I tried to free them but they were pretty firm. Didn't spend too much time though since it is going back as a core. Knowing how inexperienced the previous mechanic was, he probably never even noticed they were stuck.

 

[SabrToothSqrl]

i *think* the manual says add "1 liter" to the first tank. which is 4.2 cups... but please verify that.

 

[kleake]

Ok, I will verify in the manual. Thank you for all of the info, it is VERY much appreciated.

Waiting for a new throttle cable and impeller boot, once those are here I can finish buttoning it back up. In the mean time I still have to rebuild the carbs so i'll do that in the mean time.