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Trashed piston

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faded

faded

Active Member
1997 GSX.
SBT motor installed back in 2011. I put 100 hours on it the first year. It's been sitting for the past 3 years.
Installed a new battery and fresh fuel/oil this year and it fired right up.

Took it out yesterday and rode it for about 2 hours. Was at WOT when it simply died. No unusual noise. I thought it was out of gas. I hit the start button and it fired right up. Headed to the dock. Made it a couple hundred yards and it died again. Still no unusual noises. I did this three more times before it simply died again and wouldn't start.

Got it home and checked the fuel filter. It was all good. Try to start it and it backfired and sounded terrible. After several hours of troubleshooting the carbs I pulled the rave valves. That was when I saw the rings on one cylinder were cookied.

So now I have some questions if anyone is willing to help a guy out.

What could have caused my rings to go? Could the rave valves have possible stuck.

I pulled the cylinders and one piston is shot. The head is dented on that side. Do I just do a top end rebuild or do I drop in a whole new motor?

Can I still use the head if it has some dents in it? Or do I need to replace it as well as the cylinders and pistons?

I'm afraid there may be some small pieces of piston/rings down in my crankcase. Though I don't see any down there. Is this something I should worry about? It appears that any pieces of piston that got knocked lose may have simply been blown out the exhaust.

I can afford a new motor, if that is the best thing to do. This one has 100 hours on it. I'd hate to rebuild the top end and have the crank go out in 6 months.

Thanks for any help with this.

20170423_164334.jpg
20170423_170722.jpg
 
Did you pull the carbs to check the internal filters?

Looks like you had a lean condition on that cylinder causing it to seize (hence the engine stopping the several times).

So what to do now? I would remove the engine, tear down the top end, split the crankcase and clean it, inspect/clean the crank including bearings making sure they have no pitting or scoring and rotate freely and smoothly. Also make sure there is no bluing from overheating on the rods. You can find all clearances in the manuals. If the crank checks out and rotary valve etc. are fine, you can get away with just a top end rebuild which you can do yourself or SBT it. If crank is questionable in any way, go the SBT route as you can afford it. Personally, I like rebuilding myself so I know it's put together correctly but that's a personal decision. If you do it yourself, pressure test engine to insure no air leaks - in your case even with a top end job. Also trim the rave valves if required - if you go SBT you shouldn't have to this as I think they oversize the cylinder bore by 1mm *I think*

Real question is why did this happen and how can you keep it from happening again. Have fuel lines been replaced? What about fuel selector valve? Carb rebuild is mandatory to make sure they are clean and operating properly so that fuel is flowing. Check the oil injection system to make sure it's working, bench test the pump and replace the lines. Check the pulse line going from the crankcase to the carb to make sure it is intact with no leaks. Pull oil and fuel tanks and clean them too. Look over all vacuum and water lines and check valves while the engine is out of the ski.

Remember that any fuel sitting in the lines or carbs for a long amount of time will have ethanol that when mixed with water and interacts with the fuel lines creates a goo (after months and especially years) that will clog up your fuel system. I think if you do all the above you should be covered and it will give you a good chance at having a great running ski and get you back on the water in a few weeks.

TLDR: You have to rebuild top end at a minimum, maybe the entire engine pending inspections and findings. Clean all components of the fuel system prior to installing new engine. :thumbsup:
 
I wanted to add but couldn't edit for some reason:

As for the head, we may need more pictures to assess the damage. For the piston failure, I'm sure most of the debris was blown out the exhuast but there is more than likely contamination of the crankcase and it needs to be cleaned and inspected.
 
Thank you for the reply. It is very helpful.

The fuel lines were all changed several years ago. Selector valve was cleaned at that time. I pulled the carbs yesterday and they looked good. The filters were clean. There is oil in the lines all the way up to the carbs. When I pulled the carbs I could see oil dripping out of the oil injections ports so I assume it was getting oil. I checked all the lines fuel/oil and found no leaks.

I was going to try to get away with cheating and doing the top end without pulling the whole motor. I think after reading your reply I probably shouldn't do that. Thank you for that advice. I'll feel a lot better knowing the crank is free of debris.
 
No problem. I've recently rebuilt a 951 engine with a pto side piston seizure that looked very similar to the pictures you posted. I found the internal carb filter clogged and also found that the fitting on the carb that the fuel line attached to was clogged. The ski had been sitting for a few years when I bought it. I tore down the whole motor and inspected the bottom end - crank was okay and had not been damaged but there was debris down there that I know would have messed it up if it had continued to been run.

I would blow through every opening on the carbs so that you know everything is clear, same with the fuel lines. Something was causing no fuel/oil to reach that piston. I doubt it was the raves being stuck as that would affect performance more so than clip your rings and it would have happened by now if they weren't clearanced right. Also make sure to check that pulse line.

I know it's extra work and time and/or money to tear the whole thing down but piece of mind is really worth it, it's the right thing to do and you're making a good choice.

Keep us updated and good luck.
 
Getting ready to pull the engine and I see my crankcase has a bunch of water in it. Looks like a bunch of corrosion, scale and a weird gel like substance has clogged up my cooling ports. I'll know more and get some pictures once I get it pulled out.
 
I'm not sure if water flows through the holes in the gasket or not. There is a weird gel in the cavities behind it. I haven't pulled the manual out and looked at where the water flows to cool the engine yet. I'm not sure if this is normal or not. I still see no reason why my rings went. The damage to the piston and rings is right at the rave valve. The crank case has a cup or two of water in it.

20170428_191640.jpg

20170428_191511.jpg
 
mikidymac said:
Water don't flow through there. That is from letting salt water sit in there.
Click to expand...


It's never been in saltwater. Could the gasket have gone? Would that explain the water in the crankcase? Still trying to figure this all out.
 
Then it is nasty lake water. It is simply water, aluminum corrosion and probably bacteria.
It is caused by water sitting in the cooling passages. Are your cylinder side drain hoses plugged?
 
faded said:
I'm not sure if water flows through the holes in the gasket or not. There is a weird gel in the cavities behind it. I haven't pulled the manual out and looked at where the water flows to cool the engine yet. I'm not sure if this is normal or not. I still see no reason why my rings went. The damage to the piston and rings is right at the rave valve. The crank case has a cup or two of water in it.

View attachment 39687

View attachment 39688
Click to expand...

That's normal from sitting with water in it. Water will never drain from those cavities. The water in your crankcaes is either from when you towed it or from the cylinders when you removed them.

Chester
 
I bought a new motor and got it halfway put together when I realized there is no square broach on the end of my crankshaft for my plastic oil pump shaft to fit into. I've never heard of this motor not having this on the crankshaft. Is there some explanation as to why the shaft wouldn't have the square broach in it?

I will be calling SBT on Monday to get this straightened out.

I have looked all over online and can't seem to find any shafts that have the option to have this feature or not. I'm kind of baffled as to why it wouldn't be there.
 
Seadoo stopped using that oil pump drive some time in the late 90's and went to a black one that drives on the flywheel nut. Just order the updated black one and you will be fine. That crank was probably in a newer ski originally.
 
mikidymac said:
Seadoo stopped using that oil pump drive some time in the late 90's and went to a black one that drives on the flywheel nut. Just order the updated black one and you will be fine. That crank was probably in a newer ski originally.
Click to expand...

So I just need the updated plastic drive? Not the whole pump? Where would be the best place to find this? Thank you.
 
That is correct. As far as I know it's a dealer only item. Here is the part number 420837392 might try eBay too.
 
SBT supplies them too. I installed an SBT 787 RFI a few weeks ago for a customer and the engine he ordered came with the new oil pump drive.

Chester
 
I'm doing some research and getting mixed opinions on blocking off my oil injection. I really like that I don't have to worry about premixing but always have that lingering fear of my oil pump failing. I am going to test my oil pump as soon as I get a chance. I ordered a block off kit, just in case I decide to go premix. Wondering if anyone has any opinions on this.
 
Oil injection is the best, but you need to test the system to insure it's working properly and is varied throughout the RPM range to give the engine what it needs. Less oil at idle, high output at full throttle. You will save money in oil.

My personal opinion - if you're the only one to be gasing up and using the skis and can tell the difference between your gas cans, get rid of the oil pump and tank and go premix so you don't have to worry. May foul plugs at idle but whatever, peice of mind and less equipment. In your case, however, I believe the rotary valve still needs a supply of oil to keep it lubicated. I'll let others chime in...
 
There is no reason to get rid of it on Seadoo's. It is as reliable as they come and will save you gallons of oil.
 
mikidymac said:
There is no reason to get rid of it on Seadoo's. It is as reliable as they come and will save you gallons of oil.
Click to expand...

I haven't heard too many stories of them failing. I think I'm going to test mine and keep it.

Is there a way to rebuild them, just for piece of mind? What goes bad, when/if they do go bad? Mine has about 250ish hours on it.
 
faded said:
I haven't heard too many stories of them failing. I think I'm going to test mine and keep it.

Is there a way to rebuild them, just for piece of mind? What goes bad, when/if they do go bad? Mine has about 250ish hours on it.
Click to expand...

I haven't replaced a Seadoo oil pump in the last 20 years
 
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