2001 Seadoo Sportster LE. Just got it!

[Bonmotwang]

I think you can compare your pistons to those shown on this page:

http://www.smellofdeath.com/lloydy/piston_diag_guide.htm

It looks like an in stake seizure? from the wrong oil before?

 

[Bonmotwang]

The piston diameter is larger by the oversize amount. If the cylinder wall and piston are smooth and the clearance is within spec, the cylinder is round and not tapered within spec then you can hone the cylinder and install new rings. Also check the space between the ring and piston to see if ring lands are out of spec. The ring lands can wear also and the groove becomes too wide to make a good seal, gasses leak around the ring through the ring land groove.

Too much ring end clearance also is a leak point, place the ring inside the cylinder to measure, ring wear + cylinder wear results in large ring end gap minus the pin in the ring land that keeps ring from spinning around.

The rings will lose tension against the cylinder wall as they wear. Also, overheating can destroy the ring temper and the rings tension is lost (collapsed ring).

You are reading my mind! I am reading and study this page:

 

[Sportster-2001-951C-Stock]

Sent from my iPhone using Tapatalk

For example, this racing stripe seems to be from normal blow-by at the ring end gap.

 

[Sportster-2001-951C-Stock]

semi-trapez rings - Ah yes, the groove of piston ring land works with trapez ring to use compression in a special way, I think maybe Gordon wrote about this special type of ring in his 2-stroke tuning paper.

If you replace those rings make sure to use quality replacements, "Neither Ferrari nor us use parts from JC Whitney."

 

[Bonmotwang]

You are reading my mind! I am reading and study this page:
View attachment 26811

I am in my office right now. Will go to my boat do the measurement later.

From this picture, the end gap is huge even put it to the cylinder?

Is the piston/cylinder wall clearance the gap between the piston and skirt and cylinder wall? difference between ID of the cylinder and the OD of the piston skirt?
If this is the case then I will say my measurement will be something around 0.030". (new parts is 0.0035", wear limit is 0.008") This is based on the "push test" I did.

(gif animation uploaded did't work, so this is the jpg)

 

[Sportster-2001-951C-Stock]

It looks like an in stake seizure? from the wrong oil before?

Hmm, intake side has scoring? Difficult to say, I think water may have interfered with lubrication b/c intake area is cool then cheap oil isn't destroyed by heat?

 

[Bonmotwang]

Hmm, intake side has scoring? Difficult to say, I think water may have interfered with lubrication b/c intake area is cool then cheap oil isn't destroyed by heat?

Yes, quoted from your link

INTAKE SIDE SEIZURE
This piston was seized on the intake side. This is very uncommon and is caused by only one thing, loss of lubrication. There are three possible causes for loss of lubrication, no pre-mix oil, separation of the fuel and pre-mix oil in the fuel tank, water passed through the air-filter and washed the oil film off the piston skirt.

 

[Bonmotwang]

chatted to the PO in the afternoon. He said he didn't do anything to the boat. So it is the PPO set the carb seal off :-D

 

[Sportster-2001-951C-Stock]

I am in my office right now. Will go to my boat do the measurement later.
View attachment 26812
From this picture, the end gap is huge even put it to the cylinder?

Is the piston/cylinder wall clearance the gap between the piston and skirt and cylinder wall? difference between ID of the cylinder and the OD of the piston skirt?
If this is the case then I will say my measurement will be something around 0.030". (new parts is 0.0035", wear limit is 0.008") This is based on the "push test" I did.
View attachment 26813

You must measure ID of cylinder and OD of piston to find clearance. Ring end gap is measured by installing ring inside cylinder without piston, just use piston to push ring perpendicular into cylinder bore. I think it's difficult to use the piston if piston is attached to crankshaft, so you must use another cylindrical item of the bore size to push ring into bore and measure ring end gap. After this, subtract locating pin dimension and the result is actual ring end gap. Not sure if Rotax number includes the locating pin but I always remember a normal gap without pin is 0.010~0.020"

 

[Sportster-2001-951C-Stock]

Except, the piston is tapered normally, so did Rotax specify MAX clearance measured by subtracting average of piston taper, top of piston or bottom skirt of piston? I dunno how they measured since piston is tapered?

P^2O is the stinky guy.

 

[Bonmotwang]

You must measure ID of cylinder and OD of piston to find clearance. Ring end gap is measured by installing ring inside cylinder without piston, just use piston to push ring perpendicular into cylinder bore. I think it's difficult to use the piston if piston is attached to crankshaft, so you must use another cylindrical item of the bore size to push ring into bore and measure ring end gap. After this, subtract locating pin dimension and the result is actual ring end gap. Not sure if Rotax number includes the locating pin but I always remember a normal gap without pin is 0.010~0.020"

What is the locating pin dimension?

 

[Sportster-2001-951C-Stock]

Yes, quoted from your link

In this case could also be lack of oil too maybe but I think oil starvation causes more than just scoring of intake side. Except, the scoring was visible from the exhaust port side (RAVE slot)?

It will be interesting to see if the bore clearance is in spec., I would install new rings if possible and hone the cylinder so the new rings will seal. Of course the ring end gap must also be adjusted.

I dunno if you can measure piston diameter correctly, but you can try.

 

[Bonmotwang]

Except, the piston is tapered normally, so did Rotax specify MAX clearance measured by subtracting average of piston taper, top of piston or bottom skirt of piston? I dunno how they measured since piston is tapered?

P^2O is the stinky guy.

LOL.

If piston is tapered then it makes sense. the skirt maybe bigger, I will find out.

 

[Bonmotwang]

In this case could also be lack of oil too maybe but I think oil starvation causes more than just scoring of intake side. Except, the scoring was visible from the exhaust port side (RAVE slot)?

It will be interesting to see if the bore clearance is in spec., I would install new rings if possible and hone the cylinder so the new rings will seal. Of course the ring end gap must also be adjusted.

I dunno if you can measure piston diameter correctly, but you can try.

The scored lines exist on the opposite side too, similar condition but without yellow brown color. I should take more pictures.

 

[Sportster-2001-951C-Stock]

What is the locating pin dimension?

This is the thickness of the pin in the ring land that keeps the rings from rotating. I think you can measure this very easily. Sometimes this pin breaks and thr ring rotates until the end of ring snags inside the port opening (OUCHIE!) so if your locating pin is worn then new pistons is a very good idea despite if the bore clearance is good.

 

[Sportster-2001-951C-Stock]

Discolored (yellow) oil varnish from partially decomposed (polymerized) oil is the result from using an oil that became thermally unstable, IMO Like caramelized sugar.

 

[Bonmotwang]

This is the thickness of the pin in the ring land that keeps the rings from rotating. I think you can measure this very easily. Sometimes this pin breaks and thr ring rotates until the end of ring snags inside the port opening (OUCHIE!) so if your locating pin is worn then new pistons is a very good idea despite if the bore clearance is good.

Thanks, that was the puzzle in my mind when I was rotating the rings freely. "How do they stay in place when piston is moving at 6000PRM?"

 

[Bonmotwang]

Discolored (yellow) oil varnish from partially decomposed (polymerized) oil is the result from using an oil that became thermally unstable, IMO Like caramelized sugar.

This one is fixed by XPS-II. check

One more X for P^2O.

 

[Sportster-2001-951C-Stock]

You are only now giving the gift of the internet to refrigerators? I thought this was already done, and I could chill your beer from my chair? How is this done, microcontroller like Arduino +BT or WIFI?

 

[Bonmotwang]

Measured the piton top diameter: 87.25mm on both.
My caliper is too shallow for the skirt without remove it from the rod.

 

[Bonmotwang]

You are only now giving the gift of the internet to refrigerators? I thought this was already done, and I could chill your beer from my chair? How is this done, microcontroller like Arduino +BT or WIFI?

Designing a new main controller for my customer. They are in refrigerating business.
The system includes a touch screen on the top of the door. And refrigerator running condition is monitored online through 3D.
Lots of bells and whistles.

 

[Bonmotwang]

I think I should bring the cylinder and pistons to the dealer if I cannot confirm the piston and wall clearance is OK.
And can get a firm quote too.

 

[Sportster-2001-951C-Stock]

The scored lines exist on the opposite side too, similar condition but without yellow brown color. I should take more pictures.

Yes, even if some unusual amount of dirt entered the cylinder this will cause some abrasion to the piston. I suppose we can only guess the root cause and maybe it doesn't matter.

The carb base gasket air leak didn't help.

 

[Sportster-2001-951C-Stock]

I think I should bring the cylinder and pistons to the dealer if I cannot confirm the piston and wall clearance is OK.
And can get a firm quote too.

Since you have jumped off the bridge, it makes good sense to seek advice of an actual machinist unless you box it all up and ship it away for reman. (In that case removing the piston rings before installing the cylinder makes it easier.)

 

[Waterluvr]

I think I should bring the cylinder and pistons to the dealer if I cannot confirm the piston and wall clearance is OK.
And can get a firm quote too.

That's a sound idea, you have significant wear on the cylinders where the rings stop at TDC and reverse direction. You would be shocked to see the amount of wear on a dial bore gauge (not the type of tool I would expect you to have laying around btw ). I'm not sure the next bore size up will be enough judging from your pics.

You did a great job getting that all apart, and bottom end looks solid from you pics.

I did a few laps around the lake and spent the rest of the day on the sandbar