Valve Seals for Earlier SS Models

[abmartin]

My early '79 SS has developed a smoking habit and I'm about to change the valve seals. I'm a bit confused though. According to my information I need to replace the internal valve guide o-rings (my bike doesn't have the external lipped seals). According to several vendors the external lipped seals fit all Ducati models. Can this be right? Has anyone tried to fit the external seals to the earlier guides?

Any advice appreciated,

Bruce

[machten]

Hi Bruce,

There are two ways to create oil seal through the valves between the heads and the combustion cylinders. The original factory method for twins was soft "rubber" sleeves over the valve shafts to prevent oil running down between the guides and and valves. The early single desmos (at least) used a different method, which was an o-ring inserted inside the valve guide that sealed against the valve shaft. This has become over time, the more common way of sealing oil between the head and the combusion chamber for twins.

[quote]According to my information I need to replace the internal valve guide o-rings (my bike doesn't have the external lipped seals). Can this be right? Has anyone tried to fit the external seals to the earlier guides?[/quote]

Not sure I understand the question. The "earlier" and original twin valve guides used the rubber covers as far as I'm aware. Later after market engineering used the internal o-ring approach to seal the combustion chamber from head oil.

If it is just a case of the internal o-rings being worn or nicked then (if the guides are machined as they are usually) you can replace them with 8mm x 1mm standard viton o-rings (same size as PHF 32 choke assembly seals - but they are are nitrile)


Kev

[abmartin]

Hi Kev,

I guess what I'm trying to say is that the earlier 900SS models which include my bike weren't fitted with the external sleeve-type valve seals, at least according to my parts book. I presume Hailwoods are the same. Instead they only have the internal 0-ring seals. My question is whether anyone has retrofitted the sleeve-type seals to these earlier Super Sports since some parts suppliers say that they are suitable. I am aware that the GT models have the sleeve-type seals fitted as original equipment and that later (perhaps post '81 or so) Super Sports were fitted with guides that accepted both O-rings and sleeve-type seals.

Hope this isn't too confusing,

Bruce

[ducadini]

Both my early Darmah (9001xx) and a 860 have the internal o-ring fitted.
I've got the history of both bikes and they have not been worked on before I got them.
And my later Darmah has the external seal fitted, although I know this engine has been 'tuned'.
But the valveguides are SO worn, I'm pretty sure they haven't been changed.
So are You sure that the early ones had the external seals ??
BTW : the internal o-rings are f*é"§ing hard to change and WILL be damaged the moment You put a valve in : the small groove that has been turned in the valvestem has a sharp edge. Very difficult to get it through (although there is a method).

cu
ducadini

[abmartin]

So are You sure that the early ones had the external seals ??
BTW : the internal o-rings are f*é"§ing hard to change and WILL be damaged the moment You put a valve in : the small groove that has been turned in the valvestem has a sharp edge. Very difficult to get it through (although there is a method).

cu
ducadini

The early SS, Darmahs and Hailwoods DIDN'T have the external seals. Only the later ones and the GT models do. I'm asking whether anyone has retrofitted the external seals to the bikes that didn't originally come with them. Some dealers seem to claim that you can do this.

My idea for fitting valves through the guides with the internal seals is either to put a slight bevel around the top of the valves or else to get a piece of 8 mm rod, bevel it and then push it through the guide with the valve using lots of grease to ease the way. Any other suggestions are welcome. The factory must have worked out an efficient way of doing this.

Bruce

[machten]

Both my early Darmah (9001xx) and a 860 have the internal o-ring fitted.
I've got the history of both bikes and they have not been worked on before I got them.
And my later Darmah has the external seal fitted, although I know this engine has been 'tuned'.
But the valveguides are SO worn, I'm pretty sure they haven't been changed.
So are You sure that the early ones had the external seals ??

My apologies, I have been guilty of peddling misinformation. It was the the other way around as Ducadini points out. My 78 (which i have had since 1980 and 24,000 km) has internal seals only, and the 80/81 (not sure on the year) which I don't know the history of (but like ducadini, they are so worn I suspect are original) have both systems available.

I couldn't say if one is better than other, or if using both at the same time is good or bad. Both systems have worked OK for me on roundcases and squarecases (and singles!). I can't see that there would be any problem with retro fitting an external system as you'd still be getting some oil around the valve stem anyway, but I'm not sure there would be any benefit above an internal o-ring either.

My idea for fitting valves through the guides with the internal seals is either to put a slight bevel around the top of the valves or else to get a piece of 8 mm rod, bevel it and then push it through the guide with the valve using lots of grease to ease the way. Any other suggestions are welcome. The factory must have worked out an efficient way of doing this.

I put a light chamfer on the top of the valve and the bottom of the collet slot (just taking off the sharp edge) which seems to do the job. It doesn't affect the ability of the slot to hold the collet. The trick is to get the o-ring sitting in there without any twists or deformations. Then using plenty of oil, I push the valve though with a quick twisting motion. That seems to work fine almost every time, but I take the precaution of doing it with the head upside down over some white paper and check for any o-ring nicks on the paper after doing it. Every once in a while, I find one and have to do it again.

Kev

[wdietz186]

IIRC Ducati went to the external seals on post 77 models. They issued an update where they had you grind the bottom of the closing rocker fingers to clear the seal when the valve was open. All the replacement guides we recieved from Berliner were the external seal type but I imagine Ducati went on using what they had on hand until they ran out.

[BevHevSteve]

I have also seen and had customers tell me that they had [as early as] 1977 900SS heads with guides that had BOTH internal and cap type seals installed.. Go figure. But hey, it's a Ducati, what do you expect.

[radecal]

They were definitely the later external seal by 1982 so the change was somewhere in the early eighties but as we know there were earlier ones with the later type seal fitted.
I have converted a couple of the earlier type heads to the later seals after fitting later type valve guides. It only requires the relieving of the lower rocker arm as Wdietz 186 said and it fits perfectly. Makes a lot of sense as they are a lot easier to work with.
Bruce, if you are stuck just give me a hoy and I will shoot you my email addy.
I have about 10 heads to convert to the new type as I get to them to replace the seats to hardened ones for unleaded fuel.
Regards,