New top end cause crank to fail?????

[rob97xp]

Ok, here we go, in the last few posts with members doing new top ends, other members comment that their crank will fail. I have a 97 xp that a member on this forum rebuilt my top end. Told me my crank was nice and tight, no play. That being said, how many members have done a top end rebuild,only to have the crank fail a short time later. Everything I google on the subject comes up with water being sucked in to motor, top end rebuilt wrong, or poorly done, raves not trimmed right, and many other things, but not much on the crank...... Again I'm new to the seadoo thing, but many of my friends have done top end on their sleds, and not one has had a crank fail after top end rebuild...... Rob.

 

[68ragtop]

Here's my opinion, & it's really just that. An opinion. I think when an engine needs a top end, two things may have happen to get there. #1 The engine has a lot of hours & the top end is tired.
#2 something more catastrophic has taken place & top end parts are damaged from , bad gas, too lean, lack of oil, etc.

If someone just replaces just the top end, they might be missing another piece to the puzzle. In case #1, the bottom has hours on it too, could need seals, or have worn bearing/s. In case #2 there is more than likely debris that is strewn throughout the case & possibly into the bearings of the crank. Its also possible that leaking seals caused the top end to fail in the first place. So, that being said, its seems highly possible to have crank failure in either case after a top end if the bottom is ignored.

But, if the case is split, crank pulled out, cleaned & inspected. The bearings checked, seals replaced, runout checked, RV gear, etc. I don't see any reason the crank can't be run again.

Just my thoughts....


Every time I see a top end replaced on an engine that has considerable top end damage, & nothing else is pulled apart, I feel its a ticking time-bomb in most cases.

 

[racerxxx]

As I posted in an earlier thread:

I re-ringed my one Speedster engine 4 seasons ago, on the original crank from 99. I have no doubt in my mind--ROCK F'ING SOLID! Pasted to 7K and it never crosses my mind.

That being said. I had a water leak at the base of my PTO cylinder(leaking out, not in) so I was removing the cylinders to to replace the base gasket. I also tore down the entire engine, bead blasted the cases and everything else and checked through everything. This was done to a perfectly good running, perfect 150 PSI per hole engine. I just re-ringed it because I was already in there, it wasn't tired or blown. So it got new OEM rings and a hone job. I run the boat pretty hard sometimes, my typical crusing RPM is 5500 RPM, I like a little left in the tank if someone starts pulling up on me, or the kids tell me to hit it.

I do agree with ragtop, if you scattered parts you need to pull it down and check everything, I just assume that would be obvious. A little low on compression, probably time for a bore job, but I'd still put it back onto the old crank if it all checked out.

 

[seadoosnipe]

Here's my opinion, & it's really just that. An opinion. I think when an engine needs a top end, two things may have happen to get there. #1 The engine has a lot of hours & the top end is tired.
#2 something more catastrophic has taken place & top end parts are damaged from , bad gas, too lean, lack of oil, etc.

If someone just replaces just the top end, they might be missing another piece to the puzzle. In case #1, the bottom has hours on it too, could need seals, or have worn bearing/s. In case #2 there is more than likely debris that is strewn throughout the case & possibly into the bearings of the crank. Its also possible that leaking seals caused the top end to fail in the first place. So, that being said, its seems highly possible to have crank failure in either case after a top end if the bottom is ignored.

But, if the case is split, crank pulled out, cleaned & inspected. The bearings checked, seals replaced, runout checked, RV gear, etc. I don't see any reason the crank can't be run again.

Just my thoughts....


Every time I see a top end replaced on an engine that has considerable top end damage, & nothing else is pulled apart, I feel its a ticking time-bomb in most cases.

Excellent analogy!... There is also a step in doing a top end, that so many people seem to by-pass. You need to stick a rag or place some kind of barrier inside the casing where your jugs bolt down, to keep foreign matter out of your bottom end. Also, if the motor was original, that means the needle bearings where not caged. You need to count those to make sure you have them all. You don't have to count them if they are caged.

Also, like stated, if you have a top end failure, this could be the end result from a deeper problem. Many times, if your mag crank bearings are gone, then you'll lose the mag cylinder. I rarely do just a top end rebuild, unless I'm certain detonation or running lean was my problem. Then, if I got piston rings missing, I'll split the casing just to make sure no foreign debris fell into the lower end.

Doing an upper end rebuild is more tricky than just replacing the motor, or a complete rebuild. But, doing a complete rebuild does not mean replacing all the parts. It only means to remove and do as stated in the above post, check your run out, your back lash etc...

Hate to hear you lost a top end.

 

[Robj]

I bought a project ski that looks like someone did the top end on, too bad the crank is shot, more specifically a con rod bearing. One piston has a 1/4 inch play. It will get a full rebuild.

 

[SabrToothSqrl]

I had one and a friend had one. It's not always going to happen, but these things are 12+ years old.

I send my engines out. Full no fault warranty is the way to go.

 

[donkey]

i just bought a ski that had a "fresh "top end,(wasnt running when i bought it),atleast 1 needle brg got into the bottom end,that 1 needle brg got bounced on top of the piston,ruined the piston,jug, and head.then got stuck between the rotary valve and case,ruined the valve and shaft gear,and scooted the crank gear over.
so,the top end job killed this engine.
but,when i was pullin the engine apart,i found a ripped rotary cover seal,that had been "fixed"with rtv,(a lean condtion)
both end crank seals were leaking oil out,possible vacuum leak.so,a worn crank.
so had the topend job gone perfect,the bottom end was gonna fail soon.

 

[rob97xp]

Just to let everyone know, my crank did not fail, both my jugs had 130 on each cyclinder. Which when i took my ski to be repaired was due to a lean condition. So, now carbs are rebuilt, new fuel lines, and all new top end. I qas just wondering why every time post about doing a top end job, someone always post, your cranks gonna fail.... Rob.

 

[Minnetonka4me]

With jetskis its SOOOO much more likely a crank is going to fail b/c of the water. There is water ALL the time in the pipe. No matter how much you brapp it at the end of the day, its there. It will evaporate and eventually condensate on your nice shiny metal surfaces.

That is the reason all unknown motors should be pulled all the way apart. Out of 20 motors you would guess just need a top end, 1 or two actually have a decent crank.


And the magical fix? The #1 thing I try to preach is FOG THE MOTOR!!! After EVERY ride, or anytime its going to sit longer than 48hrs. A seadoo motor WILL last twice as long if everything else doesnt kill it first.

 

[68ragtop]

Thats a really good point. Not sure if its a common practice, but the last few times I had my skis out, I revved them for a few seconds on the trailer, pretty surprising how much water blows out of the pipe & water box. I know that doesn't get it all out, but thats got to be better than leaving a quart or so of water in there?

 

[IDoSeaDoo]

I think pressure testing the engine after you do any kind of engine work deeper than carbs is VITAL. I've solved so many of my problems by just having an engine that holds pressure. Heat is number one killer of engines, and a lean condition generates A TON of heat. Not to mention you will never be able to properly tune it. I've never had a crank fail for no reason. The one time was due to water intrusion into the cylinder, causing many little hydro-locks, as evidenced by the wet head domes and obviously ruined head gasket o-rings.

 

[Strizzo]

Thats a really good point. Not sure if its a common practice, but the last few times I had my skis out, I revved them for a few seconds on the trailer, pretty surprising how much water blows out of the pipe & water box. I know that doesn't get it all out, but thats got to be better than leaving a quart or so of water in there?

you'd be lucky if its only a quart. look at your lower portion of your pipe connected to the water box. where the exhaust exits the water box is the level where the water can get to when the engine is running before it gets blown out the exhaust outlet. when you brappp it on the trailer, the water that comes out is just what was pushed into the water box and hit the outlet to be pushed out, there is still probably 1/2 a gallon at least still in the water box/exhaust. someone else on here had the idea to pull their water box and drain it over the winter so it wouldn't corrode or become a source for engine condensation.

 

[68ragtop]

you'd be lucky if its only a quart. look at your lower portion of your pipe connected to the water box. where the exhaust exits the water box is the level where the water can get to when the engine is running before it gets blown out the exhaust outlet. when you brappp it on the trailer, the water that comes out is just what was pushed into the water box and hit the outlet to be pushed out, there is still probably 1/2 a gallon at least still in the water box/exhaust. someone else on here had the idea to pull their water box and drain it over the winter so it wouldn't corrode or become a source for engine condensation.

I'd bet just leaving the hose between the pipe & waterbox off would be a big help with condensation. Might do that at the end of this coming summer at winterizing time. Hhhmmmmm.

 

[bingle bill]

New here,
I just did a top end replacement on my 947/951.
It seemed to be going fine out of the water. After 10 minutes on the lake I got a loud squeal followed by bang. Here is a pic of where the lover let go.Would this lowere be junk now.just wounderinf before I go pulling it all apart.

 

[AdamXP800]

New here,
I just did a top end replacement on my 947/951.
It seemed to be going fine out of the water. After 10 minutes on the lake I got a loud squeal followed by bang. Here is a pic of where the lover let go.Would this lowere be junk now.just wounderinf before I go pulling it all apart.

Prime example of why everyone says "don't just throw a new top end on it."

 

[AdamXP800]

[MENTION=60523]rob97xp[/MENTION] did you get all the stuff str8 with the top end job that the member did and it failed?