Oil, lots of oil, in my airbox (Now I know why)

[stopintime]

What vintage are those crankcases and cylinders?

I think the combination of O-ring and base gasket there isn't standard.

I can see the oil squirter hole, perhaps it's plugged with debris?
..............

It's a 750, don't know the exact year.

I can't see any groove for the O-ring, be it in the cases or base gasket. It looks like an attempt to hold the O-ring in place by adding red stuff.

The red stuff and O-ring moved and was partially obstructing oil flow. How severe the oil flow was obstructed is hard to say - as you mention it's under pressure.

.......
I'm pretty sure several suitable methods were sorted out in the latter third of last century.
..........

Are you saying that Ducati is arrogant and won't admit mistakes? 

[Howie]

If memory serves me well the O rings disappeared in 2001, along with the groove for the O ring.  Mine leaked when new.  Replaced gasket, proper amount of tri bond and 60+K miles later no leak.  The S4 was more of a problem since the galley in that corner needed to be plugged.  I would suggest either do not use O rings (worked for me) or cut grooves for them.

I'm curious why that piston was running so hot, particularly since I see no signs of detonation.  What does the other piston look like?

[stopintime]

..........
  What does the other piston look like?

Don't know yet. Will report that and how the cam and rockers look, later.

[stopintime]

Well.... 

Two rockers toast (vertical head)(pictured disassembled)
Cam has some marks (vertical head)(both cam pictures are of the vertical)

Horizontal piston equally discolored
One rocker has signs of wear (but not as bad as in the vertical)
Cam, horizontal, has no marks (not pictured)

The rockers and cams were fine ~6,000 miles ago and so was the oil O-ring.

[ducpainter]

est no bueno...

[stopintime]

est no bueno...

I agree 

[koko64]

Sorry to see. Only one thing to do now, this situation has forced you to built a 100hp replacement motor .

[Speeddog]

Cam and the 3 rockers where we can see the running surface... scrap.

The color on the bottom of the horizontal piston is more than I'd want to see on a street motor.
Horizontal piston was not nearly as hot as the vertical.
Vertical was most hot on the exhaust side, which isn't much of a surprise, as that side has almost no airflow on the barrel.

I'd like to hear what ducvet thinks, he's got a big contingent of 800SS racers in his area.

Sorry to see. Only one thing to do now, this situation has forced you to built a 100hp replacement motor .

I'm pretty sure he had nearly that already.
This is the 98PS motor, yes?

[stopintime]

........

I'd like to hear what ducvet thinks, he's got a big contingent of 800SS racers in his area.

I'm pretty sure he had nearly that already.
This is the 98PS motor, yes?

Will Ducvet answer here, you think?

It is that engine, yes.

Not decided what's next.
I might repair this one, use it for another year and/or keep it as a spare.
Maybe returning it to rich mixture throughout the rev range + switching to a larger oil cooler under the horizontal head - aiding air flow to the vertical (?)

If a new tuned engine is made, it's going to have under-piston oil jets.

It's still fun with such a beast of an engine, but the constant repairs take some of it away...

[ducpainter]

If you want to get his opinion you should email him

eric at clubhousemotorsports dot com

Tell him we sent you.

[Speeddog]

~~~SNIP~~~

It's still fun with such a beast of an engine, but the constant repairs take some of it away...

I'd say that a less highly tuned 1000-based engine would be the best approach.
Wide ratio 6-speed, more efficient heads to work with, and likely cheaper to make more power than you've got now.
And it'd be a dry clutch, so your street cred goes up a bunch too.

[clubhousemotorsports]

Okay this is a can-o-worms. But lets look at some things.

Please give me a little background.
750 motor
what year?
whose pistons?
size of pistons?
miles on pistons?
use of motor (race track/street ...both)?
Rpm run?  (built motor on a 750 I would guess it lives near 8-10,000)

It appears you have the later cases with the oil jets already. This might just be the photo but if you look at the inside right above the main bearing you may see a pin hole on the left side case. On the cases I have here the vertical hole is fed by the passageway under the red screw into the left main and then squirts onto the piston.

The Horizontal pulls from a different feed, if both were equally discolored and you do have the jets then this would mean that it was unlikely one jet was blocked. Given the pictures of the red sealant in the oil feed hole you may have blockages. Do not rebuild without checking ALL passages are clear. The blockage may or may not have caused the rocker issue I have seen plenty of heads that are cooked and they often do not loose chrome but it could happen.

I have seen race pistons crack simply due to time/stresses and this is why some times a race piston is not good for a high mile bike,  some race pistons get replaced on a schedule of hours. Some brands shoot for light weight at the cost of material thickness under the dome and are more prone to crack than others. Those old school heavy forged pistons often had pretty thick domes, newer materials and processes lead many to think they can make them thinner and you can.... for a while.

The pistons we know were not cooled well and they were probably run hard and hot. There is evidence of sealant in oil passageways  (and I would check the crank) that can cause a reduction in oil flow which could lead to all kinds of problems.

The base should get a counter bore for an o-ring and NO sealant around the o-ring just the base gasket if you are using one (if not the mating surface).

depending on the year of the cases and the miles I would be tempted to swap out the cases for fresher ones as they go for short money for a small case bike and you can get some that have not been used hard. You obviously have some money tied up in that crank assembly with the rods I assume you had it all balanced as well. I would tear it all down and get the crank cleaned/inspected and the rods re-freshened (have the small ends looked at carefully that is the weak point on carillos right where you see the heat damage). get  it looked over carefully so you do not do damage to the crank /rods.

You might want to look at a s2r 800 motor and swap parts , you might be able to use your crank/rods and gain bigger valves, 6-speed and a slipper clutch with fresh cases.

[stopintime]

Thanks Eric,

my comments in yellow as we go...


750 motor
what year?
whose pistons?
size of pistons?
miles on pistons?
use of motor (race track/street ...both)?
Rpm run?  (built motor on a 750 I would guess it lives near 8-10,000)
S2R800 built at 50'km - 'everything' done - great results
At 90'km rebulit with used 10'km 750 cases, cylinders and heads - again 839cc, ported, same 6 speed, crank, rods and pistons.
Pistal pistons, very thin where they cracked - 53'km on them
Mostly street, but ~30% of yearly 20'km is spirited street and track/race
RPM... don't know what to say.. 15% at a pace that will heat to 240F - otherwise at 200F

It appears you have the later cases with the oil jets already. This might just be the photo but if you look at the inside right above the main bearing you may see a pin hole on the left side case. On the cases I have here the vertical hole is fed by the passageway under the red screw into the left main and then squirts onto the piston.
I see a pinhole there, yes

The Horizontal pulls from a different feed, if both were equally discolored and you do have the jets then this would mean that it was unlikely one jet was blocked. Given the pictures of the red sealant in the oil feed hole you may have blockages. Do not rebuild without checking ALL passages are clear. The blockage may or may not have caused the rocker issue I have seen plenty of heads that are cooked and they often do not loose chrome but it could happen.

I have seen race pistons crack simply due to time/stresses and this is why some times a race piston is not good for a high mile bike,  some race pistons get replaced on a schedule of hours. Some brands shoot for light weight at the cost of material thickness under the dome and are more prone to crack than others. Those old school heavy forged pistons often had pretty thick domes, newer materials and processes lead many to think they can make them thinner and you can.... for a while.
I really don't expect lightweight high compression pistons to last forever - at 53'km I can't complain too hard - can I?

The pistons we know were not cooled well and they were probably run hard and hot. There is evidence of sealant in oil passageways  (and I would check the crank) that can cause a reduction in oil flow which could lead to all kinds of problems.

The base should get a counter bore for an o-ring and NO sealant around the o-ring just the base gasket if you are using one (if not the mating surface).
Counterbore/groove on cases, not on base gasket - right?

depending on the year of the cases and the miles I would be tempted to swap out the cases for fresher ones as they go for short money for a small case bike and you can get some that have not been used hard. You obviously have some money tied up in that crank assembly with the rods I assume you had it all balanced as well. I would tear it all down and get the crank cleaned/inspected and the rods re-freshened (have the small ends looked at carefully that is the weak point on carillos right where you see the heat damage). get  it looked over carefully so you do not do damage to the crank /rods.
These cases, cylinders and heads are at 23'km. I'll make sure everything is checked.

You might want to look at a s2r 800 motor and swap parts , you might be able to use your crank/rods and gain bigger valves, 6-speed and a slipper clutch with fresh cases.

[clubhousemotorsports]

okay bear with me here but by 50'KM do you mean 50 Kilometers , 50,000 Kilometers or 50K(thousand) miles. Just trying to get it right. I get the feeling we are dealing with big numbers.

Pistal pistons are good pistons but yes they are pretty thin under the dome. I have not seen a set of the 90mm bore 800 pistons as our race limit is 800cc so no over bored 800's here. I have a set of 795 (90mm) pistals to compare and yes the under dome area is thin.

They are race pistons and as such they are probably not going to see much more than 8000-16,000 Km before we would change them out in a RACE BIKE. Given your street bike/track mix You should get more miles and I think you did if I am following you correctly. I would bet the motor ripped and as such it would be used as it should . High miles(Km) and race parts do not always work together and you might have found the limit on these.

Do you know when the pistons were out last case swap if the piston bottoms were as cooked?
Check the oil jets in the cases to see that they are not plugged, a combination of high miles and an over heated piston might have shortened the life. I see cooked pistons like that on old non-oil jet motors but the 750 cases you used should not have been that bad. I just checked a set of recent 800 hi comps that came out of a bike and the bottoms look new.

Do you know whose piston design they were? You might ask who you got them from how they have been holding up. We had Bruce Meyers designed Pistals (his spec.) for the most part but on some designs he would buy some one else s design of pistals. We even had a set of superbike pistons not last a weekend once, the price of R&D.

Stock pistons last........ a long time but we want more than that. Any time we ask for more there has to be a trade off. Forged pistons are stronger but then we need to make them lighter, I will always complain when something wears out/breaks because I don't want to keep re-building the same thing. All you can do is look at the replacements and guess/explore if they will last as long or longer.

Early base gaskets did not go around the oil feed o-ring, later ones did. If I am using a base gasket i like the ones with a ring around the o-ring but I do not use gasket sealer near it. The sealer can distort the o-ring and cause a leak. If you have the counter bore in the cases they should be good.

check both oil jets there should be one for each piston . all it would take is some red sealer to plug something up. I have found RTV inside crankshafts that have spun rods.

If the cases are at 23,000km then they should be fine. I have not seen the later (post 1998) small cases crack much so you should be good. I would tear it down and double check oil passages,inspect the oil pump, rebuild the crank and rods, mount up some new pistons and get back out there

[stopintime]

50'km means 50,000km (~31,000 miles), so yes, big numbers.

I didn't see the pistons during the last rebuild at 90,000km. The engine builder would have, should have, could have spoken if he noticed signs of overheating under the domes. Maybe he did, but didn't think it was necessary to replace - maybe they looked fresh. This subject will be part of the discussion about how to solve the problems.

I don't know whose design the pistons are.
They were ok from 50,000km and until the crack, at 103,000km.

Building is fun - repairing is not.
Obviously there is a fun factor in riding built and tuned engines in a 'perfect' chassis and I can't really say for sure that they don't last - I don't think any engine would run 100,000 km, with my use, without a need for rebuilding. The difference is that most riders/bikes never reach that day... and if they do, they just buy another cheap stock engine.

I think I have a pretty good idea how to deal with the O-ring now - thanks to the DMF members. Shouldn't be to hard to make it work...