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Discussion Starter #1
So... 95 Supersport 900, veetwo cams, high comp pistions....
I just did the rings as it was burning a bit of oil in the back cylinder...
Broke in the rings carefully...

Next day took it on a spin to see how it was....
Bike seemed faster... guessing the rings are okay.

But soon massive smoking out the exhaust.. like mosquito fogging truck style amounts of smoke...
Limped it home and yeah, exhaust pipe is almost dripping w oil... But-- there's also a big oil leak on the outside of the horizontal cylinder...

I assumed it was one of the 0-rings between the barrel and head had shifted- and oil was leaking both into the combustion chamber and the exterior of the cylinder.

But looking at it now.. it seems the barrel/head interface is dry, and it looks like the exterior leak was coming from the tach cable interface.......???
And it was a pretty big/high pressure leak... big slick from the tach cable all the way down the engine.

I'm about to pull the head to see if I can figure what's going on....
But was wondering if a leaky tach cable seal- could somehow dump oil into the combustion chamber???

Or am I chasing several leaks at this point?

Any ideas?
 

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I suggest you slow down and think about it. You might disassemble for no reason. Tach cable not associated with compression area.

Oil out pipe items: Head Gasket, Valve guide, Crankcase ventilation, double up on crankcase oil, broken rings. Since you blew a tach seal, I'm thinking crankcase ventilation. Don't know the motor so not sure how tach drive is positioned.

The delayed onset may indicate head gasket.
 

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My 96 kept swallowing o - rings on the return side. For some reason Ducati didn’t put any retainer to keep the o-ring from being washed into the return line cavity. I decided to solve this by installing a short piece of metal tubing to act as a inner lip . Make sure if you do this the inner diameter is large enough not to impede oil return. I then discovered the oil return in the head did not match up with the cylinder, they just overlapped each other. I was able to improve the mismatch with a die grinder, but not completely fix the issue. The mismatched galleries caused my valve cover to be excessively full of oil which was much improved after the modification, but not perfect. This can cause leaks or oil burning. I no longer use viscosity improvers because of the inadequate drain back on the horizontal cylinder/ head interface.
 

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Yes it sounds as if something has failed so check everything mentioned. I would check both to see if you have a single cylinder issue or if it is both. Unlikely to be a guide but a broken ring could cause this as could a missing or broke valve guide seal ( not a small amount of oil to cause normal valve guide oiling).

Pull valve covers and check that the returns are open as this makes sense though the oil would have to get past your valve seals and guides but if the guides and seals are old that's probably the easy part. If the returns are good and the valve guide seals are also fine you might try a leakdown test to see if you have high leakdown past the rings.
 

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Discussion Starter #5
Thanks for the beta...

So... investigating further- yeah the tach drive was def a big leak....
I just replaced both the seals in it this am... so (hopefully) scratch that off the list..

Now just a question of what happened in the hori cylinder... there's def oil residue in the chamber/on top of the piston..
But the o-ring was still in place when I pulled the head...
Also, valve guide seals are only a few days old, and they all looked intact.. so..

I used some silicone on the interface between the barrel and head when I sealed it up the other day. I'm wondering if perhaps having silicone on the regularly gasket-less surface might of lifted it a bit to allow it to leak...(?) Seems unlikely.. but I'm grasping at straws so....

At this point debating just pulling the whole motor out again and starting fresh with all new rings again..... sigh
 

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I used some silicone on the interface between the barrel and head when I sealed it up the other day
What ?

The top surface of the cylinder needs to be lapped to the inside sealing surface of the head. This is your sealing surface, if you have some material between the mating surfaces you will not have a seal between them . I am hoping you mean that there is sealer on the outer side of the cylinder flange as that should not cause a problem unless is squished between cylinder and head during assembly.

There should never be a sealer used between the head and cylinder on the non-head gasket motors, base gasket can be sealed but NOT the head/cylinders. I have seen people try and use sealer on the o-rings and that often causes a leak as well as the head/cylinder grows and the sealer will pull the o-ring out of position and you often find them leaking and twisted.
 

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Discussion Starter #7
No- I put the silicone on the flange by the oil passages.... not on the actual circular mating surface..

And I won't do it again- for fear that this might be what caused my issues...

Also- pulled off the vert cylinder exhaust-- it's oily as hell too...... dammit.

Now.. would rings that didn't bed cause the combustion chamber to be *THAT* oily??
I wonder because I really don't think I broke a ring(s) putting them in..

Just ordered another new set of rings.... so bummed to have to repeat this.. and not knowing if it'll work again this time/what I did wrong, only increases the frustration.
 

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Bummer that you have to redo what you just did - but look on the bright side - at least you have HC pistons, and don't have to pay the ridiculous price Ducati want for OEM rings!

My thought was maybe a broken oil ring or cracked piston - but both cylinders? Maybe a bad set of rings? Did you check the ring end gaps in the cylinder before you fitted them on the pistons? Check that the valve guide seals are still in place, and haven't popped off?

Good luck!
 

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This may be a dumb question and not related to the issue at hand, but what happens if there is a blockage or restriction in the external oil hoses taking oil from the cylinder back to the crankcase? Do these lines see pump pressure or is all just gravity return? If they are blocked or restricted do the oil passages start to fill any areas that normally would drain?
 

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Gravity return, unless the whole valve cover fills, which could cause oil pressure to push oil down the tube because it would have nowhere else to go ( except past the gasket ). Did you account for all the old o-rings ? Definitely clean those passages. They are small and could plug up.
 

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Does this bike have an airbox, is it full of oil?

t_bare
 

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Discussion Starter #12
Does this bike have an airbox, is it full of oil?

t_bare
No, running some pods- but the intake tubes are clean.

However, my crankcase breather was puffing out a fair amount of smoke too. And when I removed the tank etc, fair amount of oil residue on the frame etc from the breather (I've got a long hose attached to the breather that routes up to the top of the frame up by the gas tank.

But when I was doing the work, I had the engine on the bench and left it laying on it's side overnight one night, so the smoke from the cc breather, I assumed was just residual oil that flowed up to the top of the cases and was now burning off....

(of note: the engine is a '95 supersport 900, but it was transplanted into a '94 elefant a couple of years ago)
 

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Gravity return, unless the whole valve cover fills, which could cause oil pressure to push oil down the tube because it would have nowhere else to go ( except past the gasket ). Did you account for all the old o-rings ? Definitely clean those passages. They are small and could plug up.
Thanks. So does this mean that the whole head could fill with oil and because it is under pump pressure find its way up the tacho cable like is being described? :eek:
 

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I could see that happening. The seals in my tach drive were new and didn’t leak but the valve cover was completely full. After the engine sat this should have mostly drained away, in fact, it obviously needs to drain at the same rate or better than the amount being pumped in. When the chamber gets full enough I suppose it could cause more oil to go into the guides if the seals weren’t perfect. But , beyond all that, the fact that you have excess oil blowing out of the breather points to broken rings, or at least rings that aren’t sealing.
 

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Discussion Starter #16
So duc96cr, you were saying something about one of the oil returns possibly being blocked.........
I think I know why pressurized oil was shooting up though the tach cable drive.

Looks some somebody was a bit over zealous with the silicone...
 

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Keep in mind normally that is the oil feed,
Does the bike have externally fed oil lines?
 

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Yes any time you use sealer you should blow air through the oil feeds to make sure they were not plugged. If you remove the cam end cap just send some air down the oil feed hole and listen for it in the cases. Better to use less sealer around oil feeds as you do not want is sent somewhere it can plug things up. I assume you had oil in the top end so it must have been passing something.
 
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