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Dear All,

My first post, so please go easy :) Also a big thank you to all posters here for the wealth of information, it has helped me enormously so far.


I bought a 1992 900SS with 28000 miles, full fairing and non running a while ago, i got it running fairly quickly, but soon discovered that it was only running on one cylinder, as there was zero compression on the vertical cylinder.



Today i pulled the vertical cylinder, which i was happy to be able to do with only pulling the front engine bolt.

What surprised me though was that there was no gasket, i have read different advice, some saying that air cooled ducati's don't have them, yet they seem to be available to buy. So should it have a gasket? I have a feeling the previous owner has had the head off before and I may not necessarily be looking at factory.

The piston looks fine, but i think the intake the valve is bent, and the intake valve does not seat properly, hence no compression. I also found it very difficult to rotate. Here are a few pics.

I am planning to take it to an old school machine shop who know these ducati heads to get it sorted out.

If anybody has any other advice/thoughts i would appreciate any input.

A couple of pics of what I found.








Cheers

Matt
 

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I am not the resident expert on the whole gasket/no gasket debate so I can't help you there.

The polished valve face relief in the piston says the intake valve kissed it more than couple times. The offset polished crescent shape adjacent to the valve face relief looks like the intake kissed it a few more times after it bent.

The question is, why did that happen? Answer that and fix the problem before addressing the damage caused....sean
 

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I am not the resident expert on the whole gasket/no gasket debate so I can't help you there.

The polished valve face relief in the piston says the intake valve kissed it more than couple times. The offset polished crescent shape adjacent to the valve face relief looks like the intake kissed it a few more times after it bent.

The question is, why did that happen? Answer that and fix the problem before addressing the damage caused....sean
Thanks Sean, unfortunately why it happened I will never know as i bought it like this. My guess is that the belt snapped/jumped, or was put on incorrectly, as both belts were new.

I am taking the head into the machine shop today, so will see what they think.
 

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No head gasket, just metal on metal.

When the valves bend they pull the closing rocker down, which gives drag on the cam. Often a lot.

Seen a few cam pulley nuts come lose on the vertical, which lets the pulley and key flog out and then the cam gets all over the place and shit hits shit.

The original base gaskets have a hardening sealant, so you need to remove and replace it. Seal it up with three bond 1215.
 

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Only o-rings as gaskets between the head and cylinder. The true seal is the flange of the cylinder mating with the recess in the combustion chamber, these must be mated together to form a seal. You can see a slight leak (as normal) between the head stud area of the exhaust ports where combustion has been leaking by. Again normal to see but something to improve on reassembly, done by lapping cylinder to head.

Yes it looks like the intake tagged the piston so be sure to check the valve and don't forget to check the guide for cracks or other damage. Whats done is in the past but it could have been a broken belt or simply someone installed a belt 1 tooth off. Check exhaust guides while it is apart and at this point I would look at the crank plug, you have good studs already so thats good news. While apart consider a big bore as you have done much of the work and a bump in power/torque while also giving you fresh pistons and cylinders will make it a win win.

If need be also tell the wife it was caused by a lack of Keihin FCR's >:)
 

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While apart consider a big bore as you have done much of the work and a bump in power/torque while also giving you fresh pistons and cylinders will make it a win win.

If need be also tell the wife it was caused by a lack of Keihin FCR's >:)
I like your thinking :laugh:

Not sure I will get away with that though.

Anyway head now with the machine shop, I await their verdict on rebuild cost :)
 

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Listen to DucVet as I am not a Ducati expert, I am just a BMW expert lol-but hell they are both big twins--Make sure to look at not only the valve but the Guides & seats I do see guides & seats get tweeked when a valve kisses a piston. you have it apart do the job correctly --ie- do both cylinders not just the one--if a valve job is needed you might as well do both heads & cylinders the same so you have a bench mark if nothing else. at least thats my O.P.O. But if I ever say anything I will say to do the job correctly cost does not factor in for me the overall result is what matters
 

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Subscribed! Congrats on the find of a classic moto. I just sorted out my SS and she's running like a champ. My horizontal cylinder had an issue leaking oil from the exhaust port so I bought a new/used motor that is working out fine. Best of luck!
 

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Subscribed! Congrats on the find of a classic moto. I just sorted out my SS and she's running like a champ. My horizontal cylinder had an issue leaking oil from the exhaust port so I bought a new/used motor that is working out fine. Best of luck!
Many thanks, nice to hear yours is running like a champ.

Also incidentally, it has just been pointed out to me that mine is 1993 model, not a 1992. Not sure why i had 1992 in my head when i started this thread. Anyway to confirm as i just checked the registration document is is a Nov 1993.
 

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it may have been built in 92 from september onwards, but gold frame and black wheels is 93.

make sure your head shop takes the minimum required from the valve seats and faces. you can end up with shimming issues otherwise.
 
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